Técnicas quirúrgicas para la incisión y el cierre uterino en el momento de la cesárea
Resumen
Antecedentes
La cesárea es una operación frecuente. Las variaciones en la técnica dependen de la situación clínica y las preferencias del cirujano.
Objetivos
Comparar los efectos de 1) los diferentes tipos de incisión uterina, 2) los métodos para realizar la incisión uterina, 3) los materiales de sutura y la técnica del cierre uterino (incluido el cierre en capa única versus en dos capas de la incisión uterina) sobre la salud materna, la salud del lactante y el uso de recursos sanitarios.
Métodos de búsqueda
Se hicieron búsquedas en el registro de ensayos del Grupo Cochrane de Embarazo y Parto (Cochrane Pregnancy and Childbirth Group) (1 septiembre 2013) y en las listas de referencias de todos los artículos identificados.
Criterios de selección
Todos los ensayos controlados aleatorios publicados, no publicados y en curso que compararan diversos tipos de incisión y cierre uterino durante la cesárea.
Obtención y análisis de los datos
Dos revisores evaluaron los ensayos con respecto a su inclusión y la calidad metodológica sin considerar los resultados y según los criterios de elegibilidad enunciados, y extrajeron los datos de forma independiente.
Resultados principales
La estrategia de búsqueda identificó 60 estudios para su consideración, de los cuales se incluyeron en la revisión 27 ensayos aleatorios que incluyeron a 17 808 pacientes sometidas a cesárea. En términos generales, la calidad metodológica de los ensayos fue variable, 12 de los 27 ensayos incluidos describieron de forma adecuada la secuencia de asignación al azar, menos de la mitad describió de forma adecuada los métodos de ocultación de la asignación, y sólo seis ensayos indicaron el cegamiento de los evaluadores de resultado.
Dos ensayos con 300 pacientes compararon dispositivos de auto‐sutura versus histerotomía tradicional. No hubo diferencias evidentes estadísticamente significativas en la morbilidad febril entre los grupos de engrapadora y de incisión convencional (cociente de riesgos [CR] 0,92; intervalo de confianza [IC] del 95%: 0,38 a 2,20).
Se incluyeron cinco estudios con 2141 mujeres en la revisión que compararon la disección roma versus cortante al realizar la incisión uterina. No se identificaron diferencias estadísticamente significativas para el resultado primario de la morbilidad febril después de la extensión roma o cortante de la incisión uterina (cuatro estudios; 1941 pacientes; CR 0,86; IC del 95%: 0,70 a 1,05). La pérdida sanguínea media (dos estudios; 1145 pacientes; diferencia de medias [DM] promedio ‐55,00 mL; IC del 95%: ‐79,48 a ‐30,52) y la necesidad de transfusión de sangre (dos estudios; 1345 pacientes; RR 0,24, IC del 95%: 0,09 a 0,62) fueron significativamente inferiores luego de la extensión roma.
Un único ensayo con 811 mujeres comparó la extensión transversa versus la extensión roma céfalo‐caudal de la incisión uterina, y aunque se informó que la pérdida sanguínea media fue inferior luego de la extensión transversa (un estudio; 811 pacientes; DM 42,00 ml; IC del 95%: 1,31 a 82,69), la importancia clínica de una diferencia de volumen tan pequeña es de relevancia clínica incierta. No se identificó ninguna otra diferencia estadísticamente significativa para los resultados limitados informados.
Un único ensayo con 9544 pacientes que comparó el catgut crómico con poligactina‐910, informó que el cierre con catgut versus cierre con poligactina se asoció con una reducción significativa de la necesidad de transfusión de sangre (un estudio, 9544 pacientes, CR 0,49; IC del 95%: 0,32 a 0,76) y una reducción significativa de las complicaciones que requieren nueva laparotomía (un estudio, 9544 pacientes, CR 0,58; IC del 95%: 0,37 a 0,89).
Se identificaron diecinueve estudios que comparaban el cierre del útero en capa única versus en dos capas, de los cuales 14 estudios contribuyeron con datos a los metanálisis. No se identificaron diferencias estadísticamente significativas para el resultado primario, la morbilidad febril (nueve estudios; 13 890 pacientes; CR 0,98; IC del 95%: 0,85 a 1,12). Aunque el metanálisis indicó que el cierre en capa única se asoció con una reducción de la pérdida sanguínea media, la heterogeneidad es alta, lo cual limita la aplicabilidad clínica del resultado. No se identificaron diferencias en el riesgo de transfusión de sangre (cuatro estudios; 13 571 pacientes; CR promedio 0,86; IC del 95%: 0,63 a 1,17; Heterogeneidad: Tau² = 0,15; I² = 49%), u otros resultados clínicos informados.
Conclusiones de los autores
La cesárea es un procedimiento habitual al que se somete a las pacientes de todo el mundo. Hay cada vez más pruebas de que para muchas técnicas, los resultados maternos a corto plazo son equivalentes. Hasta que se conozcan los efectos sobre la salud a largo plazo, los cirujanos deben continuar utilizando las técnicas que prefieren y usan actualmente.
PICO
Resumen en términos sencillos
Técnicas quirúrgicas relacionadas con el útero en la cesárea
La cesárea es una operación abdominal frecuente para el parto quirúrgico de un feto y la placenta. Las técnicas varían según la situación clínica y las preferencias del cirujano. El parto seguro es importante para la madre y el neonato. Cualquier reducción potencial del traumatismo durante el parto en el neonato se debe equilibrar con un resultado deficiente para la salud de la madre. Los factores incluyen no sólo la duración del procedimiento quirúrgico y la pérdida sanguínea materna sino también el dolor materno posoperatorio, la pérdida sanguínea continua y el desarrollo de anemia, fiebre e infección de la herida. Las complicaciones adicionales pueden incluir problemas con la lactancia materna, al orinar, problemas de fertilidad a más largo plazo, y complicaciones en los embarazos futuros (rotura uterina) o aumento de los riesgos asociados con futuras cirugías.
Los autores de la revisión buscaron en la bibliografía médica ensayos controlados aleatorios que informaran las técnicas quirúrgicas más apropiadas a utilizar. Veintisiete ensayos que incluyeron a 17 808 pacientes de varios países diferentes contribuyeron a la revisión. Ninguno de estos ensayos evaluó el tipo de incisión uterina (incisión en el segmento uterino inferior de lado a lado [transversa] versus otros tipos de incisión uterina). Los resultados de 18 ensayos aleatorios contribuyeron a los informes de que el cierre en capa única de la incisión uterina se asoció con una reducción de la pérdida sanguínea y de la duración del procedimiento. En estos estudios el procedimiento quirúrgico para entrar en la cavidad abdominal también difirió y pudo haber contribuido a la pérdida sanguínea y la duración de la cirugía.
Cinco ensayos compararon la disección roma versus cortante en el momento de la incisión uterina (2141 pacientes) y dos ensayos adicionales compararon dispositivos de auto‐sutura con histerotomía estándar (300 pacientes). La cirugía roma se asoció con una reducción de la pérdida sanguínea media en el momento del procedimiento. El uso de un instrumento de auto‐sutura no redujo claramente la pérdida sanguínea durante el procedimiento sino que aumentó la duración del procedimiento. En términos generales, los ensayos se centraron en la pérdida sanguínea y la duración del procedimiento quirúrgico, en lugar de en resultados clínicos para las pacientes. La calidad metodológica de los ensayos era variable.
Authors' conclusions
Background
Description of the condition
Caesarean section is a common major operation performed on women in the world. Essentially, the operation involves exposing the uterus by entering the abdominal cavity through the abdominal wall. The peritoneal lining of the abdomen is opened and the peritoneum covering the uterus is usually also entered. The bladder is reflected away from the uterus to reduce the chance of damage to it during the operation. The uterus is then incised and the baby and placenta delivered. Adequate haemostasis (control of bleeding) is achieved by closure of the uterine muscle, followed by closure of the abdominal wall.
Description of the intervention
There are many possible ways of performing a caesarean section operation, and operative techniques vary widely. The techniques used may depend on many factors, including the clinical situation and the preferences of the operator. Another Cochrane review providing an overview of the techniques, indications for caesarean section and postoperative complications, has been published (Hofmeyr 2008).
Our review specifically assessed surgical techniques involving the uterus at the time at caesarean section, and included:
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the type of uterine incision (lower transverse uterine incision versus other types of uterine incision);
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methods of performing the uterine incision ('sharp' uterine entry versus 'blunt' uterine entry);
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suturing materials and techniques for the uterus at caesarean section; and
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single versus double layer suturing for closing the uterine incision at caesarean section.
How the intervention might work
Part one: type of uterine incision at caesarean section
Part one of this review compares the outcomes of caesarean sections performed using a transverse lower segment uterine incision with other types of uterine incision (low vertical, 'classical', T‐shaped or J‐shaped incision).
The transverse (side‐to‐side) lower segment uterine incision is widely used in obstetric practice today. This incision has been favoured because the lower uterine segment is less vascular than the body of the uterus, and the incision is easier to repair. This leads to a reduction in operative complications, especially haemorrhage, and also a reduction in morbidity. Lower segment incisions are also associated with a lower incidence of uterine dehiscence or rupture in subsequent pregnancies (Tahilramaney 1984).
The use of a low vertical uterine incision has been recommended in certain clinical situations, particularly in delivery of the preterm infant, where the lower uterine segment may be poorly formed and the longitudinal incision may facilitate delivery and reduce birth trauma by improved surgical access.
A 'classical' uterine incision involves a vertical (up and down cut) in the upper body of the uterus, and is used more rarely. It may be used when the baby is in a transverse lie (that is, lying across the mother's uterus), when the infant is preterm, or if there is an anterior placenta praevia (the placenta lies in the lower segment and on the front wall of the uterus where the lower transverse uterine incision is usually made), but in practice, this incision is rarely used. Haemorrhage is potentially more severe when an upper uterine segment incision is used, and the repair often requires closure in three layers as the myometrium (uterine muscle) is thicker in this part of the uterus.
Occasionally, a transverse lower segment incision is made, and during the operation, the incision needs to be extended in order to obtain better surgical access, or to facilitate delivery of the infant. In these situations, the incision may be extended vertically in the midline, into the upper segment of the uterus forming an inverted (upside‐down) T‐shaped incision. Alternatively, the incision may be extended vertically from the end of the transverse incision to form a J‐shaped incision.
Potential injuries that may occur for the infant during a traumatic caesarean birth include fractures, peripheral nerve damage, spinal cord injury and subdural haematoma. Any potential reduction of birth trauma to the infant has to be balanced against potential increased morbidity to the mother such as operative blood loss and postoperative complications. In particular, consideration needs to be given to mode of birth in any subsequent pregnancy. Uterine rupture is a significant risk in a subsequent pregnancy or labour, with estimates of occurrence being 4% to 9% for classical (uterine body, midline) caesarean incision; 4% to 9% for inverted T‐shaped incisions; 1% to 7% for lower uterine segment vertical incisions; and 0.2% to 1.5% for lower uterine segment transverse incisions (ACOG 1999). Current ACOG guidelines limit trial of vaginal birth after caesarean section to women with a lower uterine segment transverse incision, and recommend repeat caesarean birth for women with a prior classical or inverted T‐shaped uterine scar (ACOG 1999). Any consideration of the benefits associated with a particular uterine incision must also consider the longer‐term risks associated with repeat caesarean.
Part two: methods of performing the uterine incision
Part two of this review compares the outcomes of caesarean sections performed using different methods of incising the uterus (including autostapling and sharp and blunt uterine entry).
When the uterus is incised at the time of caesarean section, the incision may be made in the centre of the lower uterine segment with a scalpel and then extended laterally with scissors ('sharp' uterine entry) or by digital extension (using the fingers) ('blunt' uterine entry). There has been ongoing debate about which of these forms of entry results in better maternal and infant outcomes (Rodriguez 1994). Theoretical benefits of sharp uterine entry include more rapid delivery of the baby, and a more controlled entry, with less likelihood of the incision extending into the broad ligament or uterine vessels. The 'clean' incision may also be easier to repair. Proponents of blunt uterine entry argue that following the tissue planes reduces blood loss and improves healing, and that dispensing with an instrument improves control over the entry.
Autostapling techniques involve the insertion of staples as the surgical incision is made in order to keep the operating field as bloodless as possible (Wilkinson 2006). The Auto Suture Poly CS 57 Stapler was developed in the early 1990s. Its aim was to achieve haemostasis through the placement of a double layer of absorbable sutures before the uterine incision was made. The technique may be useful in particular circumstances, for example, where the woman is infected with HIV, reducing contamination with maternal blood and potentially reducing viral transmission to the infant.
Part three: suturing materials and techniques for the uterus
Part three of this review compares the outcomes of caesarean sections performed using different materials and techniques for closure of the uterine incision.
There are a range of suture materials and techniques used in surgical procedures, with the choice often resting with the preference of the operator. For example, some advocate a single continuous suture to close the uterus, which can be locked or not locked. Others advocate multiple or interrupted sutures. Depending on local resources and preference, different types of suture including monofilament and polyfilament/multifilament may be used to close the uterus.
Part four: single versus double layer suturing for closing the uterine incision
Part four of this review compares the outcomes of caesarean sections performed using single layer closure of the uterine incision with those using double layer closure.
One specific question about the technique used for uterine closure is whether it should be closed with one layer of sutures or two. Traditionally, the transverse lower segment uterine incision is closed in two layers (Enkin 2006). Those who advocate double closure of the uterus cite improved haemostasis and wound healing, and possibly a reduced risk of uterine rupture in a subsequent pregnancy. Single layer closure may be associated with reduced operating time, less tissue disruption, and less introduction of foreign suture material into the wound. These potential advantages may translate into reduced operative and postoperative morbidity for women. However, a recent observational study from Canada has suggested that single layer closure of the lower uterine segment at caesarean section is associated with a four‐fold increase in the risk of uterine rupture in a subsequent pregnancy when compared with double layer uterine closure (odds ratio 3.95, 95% confidence interval 1.35 to 11.49) (Bujold 2002).
Why it is important to do this review
Caesarean section is a common operation, with many different methods of performing the surgery. It is important to assess the benefits and harms associated with these different ways of performing the surgery.
Objectives
To compare, using the best available evidence, the effects of:
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different types of uterine incision;
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different methods of performing the uterine incision;
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different materials and techniques for closure of the uterine incision; and
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single versus double layer closure of the uterine incision on maternal or infant health, or both, and health care resource use.
Methods
Criteria for considering studies for this review
Types of studies
All published, unpublished, and ongoing randomised controlled trials comparing various types of uterine incision and closure of the uterine incision during caesarean section.
We excluded quasi‐randomised trials (e.g. those randomised by date of birth or hospital number) from the analysis. Studies presented in abstract form only will not be included until the full report becomes available to assess methodological quality and relevance to the scope of the review.
Types of participants
Women undergoing caesarean birth.
Types of interventions
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Transverse lower uterine segment incision versus other types of uterine incision.
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Methods of performing the uterine incision (including 'sharp' versus 'blunt' uterine entry; absorbable sutures versus scissor or digital extension; direction of dissection (transverse versus cephalad‐caudad)).
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Different materials or techniques, or both, for closure of the uterine incision (including continuous suture versus interrupted suture).
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Single versus double layer closure of the uterine incision.
Types of outcome measures
Primary outcomes
Postoperative febrile morbidity (as defined by trial authors).
Secondary outcomes
Outcome measures for the woman
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Postoperative analgesia requirements (as defined by trial authors).
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Blood loss (as defined by trial authors).
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Maternal death or serious maternal morbidity (e.g. admission to intensive care unit).
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Need for blood transfusion.
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Wound infection (as defined by trial authors).
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Wound complications (e.g. operative procedures carried out on the wound; wound haematoma).
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Postoperative pain (as measured by visual analogue scale or need for additional analgesia).
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Breastfeeding (at hospital discharge, or as defined by trial authors).
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Voiding problems (as defined by trial authors).
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Duration of surgery.
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Postoperative anaemia (as defined by trial authors).
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Thromboembolic disease.
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Complications during the postoperative period requiring further surgery (re‐laparotomy).
Longer‐term outcome measures for the woman
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Future fertility problems.
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Complications in a future pregnancy (e.g. placenta praevia, placenta accreta, uterine rupture).
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Complications at future surgery (e.g. adhesion formation).
Outcome measures for the infant (applicable to part one and two of the review)
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Neonatal death.
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Birth trauma (as defined by trial authors).
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Infant laceration.
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Admission to neonatal intensive care unit and length of stay.
Health service use
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Length of postoperative stay for the woman and infant.
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Readmission to hospital of the woman or infant, or both.
Only outcomes with available data appear in the analysis table. Only outcome data that were prestated by the review authors have been used.
The methods section of this review is based on a standard template used by the Cochrane Pregnancy and Chilbirth Group.
Search methods for identification of studies
Electronic searches
We searched the Cochrane Pregnancy and Childbirth Group’s Trials Register by contacting the Trials Search Co‐ordinator (1 September 2013).
The Cochrane Pregnancy and Childbirth Group’s Trials Register is maintained by the Trials Search Co‐ordinator and contains trials identified from:
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monthly searches of the Cochrane Central Register of Controlled Trials (CENTRAL);
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weekly searches of MEDLINE;
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weekly searches of Embase;
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handsearches of 30 journals and the proceedings of major conferences;
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weekly current awareness alerts for a further 44 journals plus monthly BioMed Central email alerts.
Details of the search strategies for CENTRAL, MEDLINE and Embase, the list of handsearched journals and conference proceedings, and the list of journals reviewed via the current awareness service can be found in the ‘Specialized Register’ section within the editorial information about the Cochrane Pregnancy and Childbirth Group.
Trials identified through the searching activities described above are each assigned to a review topic (or topics). The Trials Search Co‐ordinator searches the register for each review using the topic list rather than keywords.
Searching other resources
We conducted a manual search of the reference lists of all identified papers.
We did not apply any language restrictions.
Data collection and analysis
For the methods used when assessing the trials identified in the previous version of this review, seeAppendix 1.
For this update we used the following methods when assessing the reports identified by the updated search.
Selection of studies
Two review authors independently assessed for inclusion all the potential studies we identified as a result of the search strategy. We resolved any disagreement through discussion or, if required, we consulted a third person.
Data extraction and management
We designed a form to extract data. For eligible studies, two review authors extracted the data using the agreed form. We resolved discrepancies through discussion or, if required, we consulted a third person. We entered data into Review Manager software (RevMan 2012) and checked it for accuracy.
When information regarding any of the above was unclear, we planned to contact authors of the original reports to provide further details.
Assessment of risk of bias in included studies
Two review authors independently assessed risk of bias for each study using the criteria outlined in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). We resolved any disagreement by discussion or by involving a third assessor.
(1) Random sequence generation (checking for possible selection bias)
We described for each included study the method used to generate the allocation sequence in sufficient detail to allow an assessment of whether it should produce comparable groups.
We assessed the method as:
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low risk of bias (any truly random process, e.g. random number table; computer random number generator);
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high risk of bias (any non‐random process, e.g. odd or even date of birth; hospital or clinic record number);
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unclear risk of bias.
(2) Allocation concealment (checking for possible selection bias)
We described for each included study the method used to conceal allocation to interventions prior to assignment and assessed whether intervention allocation could have been foreseen in advance of, or during recruitment, or changed after assignment.
We assessed the methods as:
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low risk of bias (e.g. telephone or central randomisation; consecutively numbered sealed opaque envelopes);
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high risk of bias (open random allocation; unsealed or non‐opaque envelopes, alternation; date of birth);
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unclear risk of bias.
(3.1) Blinding of participants and personnel (checking for possible performance bias)
We described for each included study the methods used, if any, to blind study participants and personnel from knowledge of which intervention a participant received. We considered that studies were at low risk of bias if they were blinded, or if we judged that the lack of blinding was unlikely to affect results. We assessed blinding separately for different outcomes or classes of outcomes.
We assessed the methods as:
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low, high or unclear risk of bias for participants;
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low, high or unclear risk of bias for personnel.
(3.2) Blinding of outcome assessment (checking for possible detection bias)
We described for each included study the methods used, if any, to blind outcome assessors from knowledge of which intervention a participant received. We assessed blinding separately for different outcomes or classes of outcomes.
We assessed methods used to blind outcome assessment as:
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low, high or unclear risk of bias.
(4) Incomplete outcome data (checking for possible attrition bias due to the amount, nature and handling of incomplete outcome data)
We described for each included study, and for each outcome or class of outcomes, the completeness of data including attrition and exclusions from the analysis. We stated whether attrition and exclusions were reported and the numbers included in the analysis at each stage (compared with the total randomised participants), reasons for attrition or exclusion where reported, and whether missing data were balanced across groups or were related to outcomes. Where sufficient information was reported, or could be supplied by the trial authors, we planned to re‐include missing data in the analyses which we undertook.
We assessed methods as:
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low risk of bias (e.g. no missing outcome data; missing outcome data balanced across groups);
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high risk of bias (e.g. numbers or reasons for missing data imbalanced across groups; ‘as treated’ analysis done with substantial departure of intervention received from that assigned at randomisation);
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unclear risk of bias.
(5) Selective reporting (checking for reporting bias)
We described for each included study how we investigated the possibility of selective outcome reporting bias and what we found.
We assessed the methods as:
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low risk of bias (where it is clear that all of the study’s pre‐specified outcomes and all expected outcomes of interest to the review have been reported);
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high risk of bias (where not all the study’s pre‐specified outcomes have been reported; one or more reported primary outcomes were not pre‐specified; outcomes of interest are reported incompletely and so cannot be used; study fails to include results of a key outcome that would have been expected to have been reported);
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unclear risk of bias.
(6) Other bias (checking for bias due to problems not covered by (1) to (5) above)
We described for each included study any important concerns we had about other possible sources of bias.
We assessed whether each study was free of other problems that could put it at risk of bias:
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low risk of other bias;
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high risk of other bias;
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unclear whether there is risk of other bias.
(7) Overall risk of bias
We made explicit judgements about whether studies were at high risk of bias, according to the criteria given in the Handbook (Higgins 2011). With reference to (1) to (6) above, we assessed the likely magnitude and direction of the bias and whether we considered it likely to impact on the findings. We planned to explore the impact of the level of bias through undertaking sensitivity analyses ‐ seeSensitivity analysis.
Measures of treatment effect
Dichotomous data
For dichotomous data, we presented results as summary risk ratio with 95% confidence intervals.
Continuous data
For continuous data, we used the mean difference if outcomes were measured in the same way between trials. In future updates, if appropriate, we will use the standardised mean difference to combine trials that measure the same outcome, but use different methods.
Unit of analysis issues
Cluster‐randomised trials
We planned to include cluster‐randomised trials in the analyses along with individually‐randomised trials. No cluster‐randomised trials were identified for this update. In future updates, if identified and analysed, we will adjust their sample sizes using the methods described in the Handbook [Section 16.3.4] using an estimate of the intracluster correlation co‐efficient (ICC) derived from the trial (if possible), from a similar trial or from a study of a similar population. If we use ICCs from other sources, we will report this and conduct sensitivity analyses to investigate the effect of variation in the ICC. If we identify both cluster‐randomised trials and individually‐randomised trials, we plan to synthesise the relevant information. We will consider it reasonable to combine the results from both if there is little heterogeneity between the study designs and the interaction between the effect of intervention and the choice of randomisation unit is considered to be unlikely.
We will also acknowledge heterogeneity in the randomisation unit and perform a sensitivity analysis to investigate the effects of the randomisation unit.
Cross‐over trials
Cross‐over trials are not an appropriate study design for the interventions considered in this review.
Dealing with missing data
For included studies, we noted levels of attrition. We planned to explore the impact of including studies with high levels of missing data in the overall assessment of treatment effect by using sensitivity analysis.
For all outcomes, we carried out analyses, as far as possible, on an intention‐to‐treat basis, i.e. we attempted to include all participants randomised to each group in the analyses, and all participants were analysed in the group to which they were allocated, regardless of whether or not they received the allocated intervention. The denominator for each outcome in each trial was the number randomised minus any participants whose outcomes were known to be missing.
Assessment of heterogeneity
We assessed statistical heterogeneity in each meta‐analysis using the Tau², I² and Chi² statistics. We regarded heterogeneity as substantial if an I² was greater than 30% and either a Tau² was greater than zero, or there was a low P value (less than 0.10) in the Chi² test for heterogeneity.
Assessment of reporting biases
For this update, there were not more than 10 studies in any meta‐analysis. In future updates, if there are 10 or more studies in the meta‐analysis, we will investigate reporting biases (such as publication bias) using funnel plots. We will assess funnel plot asymmetry visually. If asymmetry is suggested by a visual assessment, we will perform exploratory analyses to investigate it.
Data synthesis
We carried out statistical analysis using the Review Manager software (RevMan 2012). We used fixed‐effect meta‐analysis for combining data where it was reasonable to assume that studies were estimating the same underlying treatment effect: i.e. where trials were examining the same intervention, and the trials’ populations and methods were judged sufficiently similar. If there was clinical heterogeneity sufficient to expect that the underlying treatment effects differed between trials, or if substantial statistical heterogeneity was detected, we used random‐effects meta‐analysis to produce an overall summary, if an average treatment effect across trials was considered clinically meaningful. The random‐effects summary was treated as the average range of possible treatment effects and we discussed the clinical implications of treatment effects differing between trials. If the average treatment effect was not clinically meaningful, we did not combine trials.
If we used random‐effects analyses, the results were presented as the average treatment effect with 95% confidence intervals, and the estimates of Tau² and I².
Subgroup analysis and investigation of heterogeneity
We did not carry out subgroup analysis for this update.
In future updates, if we identify substantial heterogeneity, we will investigate it using subgroup analyses and sensitivity analyses. We will consider whether an overall summary is meaningful, and if it is, use random‐effects analysis to produce it.
We plan to carry out the following subgroup analyses.
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Planned (elective procedure, not in labour) versus emergency procedures (procedures performed in labour, including those women that had intended an 'elective operation" and now in spontaneous labour).
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Primary versus subsequent caesarean section procedure.
Only the primary outcome will be used in subgroup analysis.
We will assess subgroup differences by interaction tests available within RevMan (RevMan 2012). We will report the results of subgroup analyses quoting the Chi² statistic and P value, and the interaction test I² value.
Sensitivity analysis
We planned to carry out sensitivity analyses to explore the effect of trial quality assessed by concealment of allocation, high attrition rates (greater than 20%), or both, with poor‐quality studies being excluded from the analyses in order to assess whether this made any difference to the overall result.
Results
Description of studies
Results of the search
The search strategy identified 60 studies for consideration in this review.
Included studies
Twenty‐seven randomised controlled trials, involving 17,808 women undergoing caesarean section were included in this review (Batioglu 1998; Bjorklund 2000; CAESAR 2010; Ceci 2012; CORONIS 2013; Chitra 2004; Cromi 2008; Dani 1998; Darj 1999; Ferrari 2001; Gutierrez 2008; Hamar 2007; Hauth 1992; Hidar 2007; Lal 1988; Magann 2002; Moreira 2002; Poonam 2006; Rodriguez 1994; Sekhavat 2010; Sood 2005; Studzinski 2002; Villeneuve 1990; Von Rechenberg 1990; Wallin 1999; Xavier 2005; Yasmin 2011). Information related to longer‐term follow‐up of women was available from the Hauth paper (Chapman 1997) for the Hauth 1992 trial.
Types of uterine incision (transverse lower uterine segment incision versus other types of uterine incision)
There were no studies identified making this comparison in relation to type of uterine incision.
Methods of performing the uterine incision (including 'sharp' versus 'blunt' uterine entry; absorbable sutures versus scissor or digital extension; direction of blunt dissection: transverse versus cephalad‐caudad)
Five studies were included in the review making the comparison between methods of performing the uterine incision (Hidar 2007; Magann 2002; Poonam 2006; Rodriguez 1994; Sekhavat 2010). All compared blunt versus sharp dissection at the time of uterine incision, involving women from the United States (Magann 2002; Rodriguez 1994), Tunisia (Hidar 2007), Nepal (Poonam 2006), and Iran (Sekhavat 2010). Two studies were identified involving the use of the Autosuture Poly CS 57 automatic surgical stapler compared with standard hysterotomy, involving women from Canada (Villeneuve 1990) and Switzerland (Von Rechenberg 1990). A single study compared the direction of blunt extension of the uterine incision (transverse versus cephalad‐caudad), involving women from Italy (Cromi 2008). All studies were single centre.
Different materials or techniques, or both, for closure of the uterine incision (including continuous suture versus interrupted suture)
One study was identified that compared continuous suture closure with interrupted suture closure of the uterine incision (Ceci 2012). Women were followed until 24 months postpartum but only ultrasound and hysteroscopic assessments were reported. One study was identified that compared two different types of material for closure of the uterine incision (CORONIS 2013). In this study, chromic catgut was compared with number 1 polygactin‐910 in almost 10,000 women (this closure could be with interrupted or continuous sutures).
Single versus double layer closure of the uterine incision
Nineteen studies were identified comparing single layer with double layer closure of the uterus (Batioglu 1998; Bjorklund 2000; CAESAR 2010; CORONIS 2013; Chitra 2004; Dani 1998; Darj 1999; Ferrari 2001; Gutierrez 2008; Hamar 2007; Hauth 1992; Lal 1988; Moreira 2002; Poonam 2006; Sood 2005; Studzinski 2002; Wallin 1999; Yasmin 2011; Xavier 2005). These studies were conducted in Tanzania (Bjorklund 2000), Tunisia (Hidar 2007), Senegal (Moreira 2002), the United Kingdom (CAESAR 2010), United States of America (Hamar 2007; Hauth 1992), India (Chitra 2004; Lal 1988; Sood 2005), Nepal (Poonam 2006), Mexico (Gutierrez 2008), Turkey (Batioglu 1998), Italy (CAESAR 2010; Dani 1998; Ferrari 2001), Poland (Studzinski 2002), Senegal (Moreira 2002), Portugal (Xavier 2005), and Sweden (Darj 1999; Wallin 1999). With the exception of the CAESAR study (CAESAR 2010), and the CORONIS study (CORONIS 2013), all were single centre. The study by Yasmin and colleagues (Yasmin 2011) focused on ultrasound follow‐up of the uterine scar, outcomes which were not pre‐specified in this review. The study by Dani and colleagues (Dani 1998) reported short‐term infant outcomes after caesarean section, but none of these outcomes were prespecified in the review.
For details of the included studies, see the table of Characteristics of included studies.
Excluded studies
Twenty‐six studies were excluded from the review, with 14 studies using quasi‐randomised methods of treatment allocation (Ansaloni 2001; Baxter 2008; Behrens 1997; Dargent 1990; Falls 1958; Gaucherand 2001; Hameed 2004; Heidenreich 1995; Hoskins 1991; Kiefer 2008; Lodh 2002; Ohel 1996; Redlich 2001; Van Dongen 1989; ). Eleven studies were excluded as the comparisons did not involve surgical techniques on the uterus (Buhimschi 2006; Decavalas 1997; Doganay 2010; Gedikbasi 2011; Ghezzi 2001; Giacalone 2002; Hohlagschwandtner; Malvasi 2011; Moroz 2008; Naki 2011; Ozbay 2011). One study did not utilise intention‐to‐treat principles for data analysis, and it was not possible from the information provided to restore participants to their randomised groups (Heimann 2000).
For details of the excluded studies, see the table of Characteristics of excluded studies.
Studies awaiting assessment and ongoing studies
Several reports were identified in abstract form only, with insufficient information available to allow assessment for inclusion in this review (Borowski 2007; Hagen 1999; Mazhar 2004; Mukhopadhyay 2000; Pandey 2006; Wojdemann 2010); another trial report is in Polish and is awaiting translation (Belci 2005) (see Studies awaiting classification), In addition, we identified one trial registration (Farajzadeh 2010) (see Characteristics of ongoing studies).
Risk of bias in included studies
Overall, the methodological quality of the trials was variable (see Description of studies and Characteristics of included studies). There was variable reporting of the prespecified outcomes of the review, with 21 trials presenting information that could be incorporated into the meta‐analysis (Batioglu 1998; Bjorklund 2000; CAESAR 2010; CORONIS 2013; Chitra 2004; Cromi 2008; Ferrari 2001; Gutierrez 2008; Hamar 2007; Hauth 1992; Hidar 2007; Magann 2002; Moreira 2002; Poonam 2006; Rodriguez 1994; Sekhavat 2010; Studzinski 2002; Villeneuve 1990; Von Rechenberg 1990; Wallin 1999; Xavier 2005).
SeeFigure 1; and Figure 2 for a summary of 'Risk of bias' assessments.
'Risk of bias' graph: review authors' judgements about each risk of bias item presented as percentages across all included studies.
'Risk of bias' summary: review authors' judgements about each risk of bias item for each included study.
Allocation
While all of the studies were stated to be randomised, the method of randomisation was adequately described in 13 trials as involving either computer‐generated randomisation sequences or tables of random numbers (Bjorklund 2000; CAESAR 2010; Ceci 2012; CORONIS 2013; Cromi 2008; Hauth 1992; Hidar 2007; Magann 2002; Sekhavat 2010; Sood 2005; Villeneuve 1990; Wallin 1999; Xavier 2005). The method of allocation concealment was assessed as adequate in 13 trials, with 11 utilising sequentially numbered, sealed, opaque envelopes (Bjorklund 2000; Darj 1999; Ferrari 2001; Hamar 2007; Hauth 1992; Hidar 2007; Magann 2002; Sekhavat 2010; Sood 2005; Villeneuve 1990; Wallin 1999), and two telephone randomisation (CAESAR 2010; CORONIS 2013).
Blinding
Blinding of outcome assessor was indicated in only six of the trials (CAESAR 2010; Ceci 2012; Dani 1998; Sood 2005; Wallin 1999; Xavier 2005). Blinding of both participants and personnel was not indicated in any of the included trials. Participants were blinded in one trial (Sekhavat 2010).
Incomplete outcome data
Most included studies were assessed as at low risk of bias due to incomplete outcome data, with three being assessed as unclear risk.
Selective reporting
Most included studies were assessed as at low risk of bias for selective reporting, however, four studies were assessed as having an unclear risk of selective reporting bias.
Other potential sources of bias
The CEASAR trial was identified as at potential risk of bias, having modified the primary outcome of the trial after 600 women were recruited, and as the trial was stopped short of the total estimated sample size (CAESAR 2010). The trial by Xavier (Xavier 2005) recruited and randomised 162 women, with outcome data reported for only 72.
Effects of interventions
Twenty‐seven randomised controlled trials, involving 17,808 women undergoing caesarean section were included in this review, as described below.
Methods of performing the uterine incision (including 'sharp' versus 'blunt' uterine entry and absorbable sutures versus scissor or digital extension)
Automatic stapler versus conventional uterine incision
Two trials (Villeneuve 1990; Von Rechenberg 1990) compared auto‐suture devices with traditional hysterotomy involving 300 women. It was only possible to combine data from the two trials included for the primary outcome, febrile morbidity. No statistically significant difference between the stapler and conventional incision groups was apparent (risk ratio (RR) 0.92, 95% confidence interval (CI) 0.38 to 2.20), Analysis 1.1. Other outcomes included data from only one study. There is a suggestion of a lower blood loss in the stapler group in Villeneuve 1990 (mean difference (MD) ‐87.00 mL, 95% CI ‐175.09 to 1.09), Analysis 1.2; however, the lack of blinding means that bias in the assessment of this outcome cannot be excluded.
Blunt versus sharp extension of the uterine incision
Five trials compared blunt with sharp extension of the uterine incision, involving 2141 women (Hidar 2007; Magann 2002; Poonam 2006; Rodriguez 1994; Sekhavat 2010). There were no statistically significant differences identified for the primary outcome febrile morbidity following blunt or sharp extension of the uterine incision (four studies; 1941 women; RR 0.86; 95% CI 0.70 to 1.05), Analysis 2.1. Mean blood loss (two studies; 1145 women; average MD ‐55.00 mL; 95% CI ‐79.48 to ‐30.52; Heterogeneity: Tau² = 160.80; I² = 51%), Analysis 2.2, and the need for blood transfusion (two studies; 1345 women; RR 0.24; 95% CI 0.09 to 0.62), Analysis 2.3, were significantly lower following blunt extension, with no other significant differences identified in duration of operative procedure (one study; 200 women; MD ‐2.80 minutes; 95% CI ‐5.84 to 0.24), Analysis 2.5, or risk of serious maternal morbidity (one study; 400 women; RR 3.00; 95% CI 0.12 to 73.20), Analysis 2.4.
Direction of blunt extension of the uterine incision: transverse versus cephalad‐caudad
A single trial compared transverse with cephalad‐caudad blunt extension of the uterine incision, involving 811 women (Cromi 2008). While mean blood loss was reported to be lower following transverse extension (one study; 811 women; MD 42.00 mL; 95% CI 1.31 to 82.69), Analysis 3.1, the clinical significance of such a small volume difference is of uncertain clinical relevance. There were no other statistically significant differences identified for the limited outcomes reported.
Single versus double layer closure of the uterine incision
Nineteen studies were identified comparing single layer with double layer closure of the uterus (Batioglu 1998; Bjorklund 2000; CAESAR 2010; CORONIS 2013; Chitra 2004; Dani 1998; Darj 1999; Ferrari 2001; Gutierrez 2008; Hamar 2007; Hauth 1992; Lal 1988; Moreira 2002; Poonam 2006; Sood 2005; Studzinski 2002; Wallin 1999; Yasmin 2011; Xavier 2005), with data contributed to the meta‐analyses from 14 studies. The reported standard deviations for continuous variables reported in Ferrari 2001 were considered to be far too small to be plausible, and we believe that the authors have erroneously reported standard errors rather than standard deviations. We have therefore, converted the standard errors to standard deviations by dividing the square root of the sample size for inclusion of these data in the analyses.
There were no statistically significant differences identified for the primary outcome, febrile morbidity (nine studies; 13,890 women; RR 0.98; 95% CI 0.85 to 1.12), Analysis 4.1. For the outcome of mean blood loss, although the meta‐analysis suggested single layer closure sure was associated with a reduction in mean blood loss, heterogeneity is high and this limits the clinical applicability of the result. There were no differences identified in risk of blood transfusion (four studies; 13,571 women; average RR 0.86; 95% CI 0.63 to 1.17; Heterogeneity: Tau² = 0.03; I² = 30%), Analysis 4.3. There were no other significant differences identified in the reported clinical outcomes.
Suturing materials and techniques for uterine closure (including continuous suture versus interrupted suture)
One study was identified that compared continuous versus interrupted suture closure for the uterine incision (Ceci 2012), however, no clinical maternal outcomes were reported, with ultrasound and hysteroscopic assessments forming the main focus of the paper. The single trial comparing chromic catgut with polygactin‐910 reported on outcomes in 9544 women (CORONIS 2013) . Closure with catgut was associated with a significant reduction in the need for blood transfusion (one study, 9544 women, RR 0.49, 95% CI 0.32 to 0.76), Analysis 5.2. and a significant reduction in complications requiring re‐laparotomy (one study, 9544 women, RR 0.58, 95% CI 0.37 to 0.89); Analysis 5.6. There were no other significant differences in the other reported outcomes.
It was not possible to conduct the planned subgroup analyses.
Discussion
Summary of main results
While caesarean section is a common procedure performed on women worldwide, there is limited information available to inform the most appropriate surgical technique to adopt. Our review did not identify any randomised controlled trials assessing the type of uterine incision to be used (transverse lower uterine segment incision versus other types of uterine incision), the materials used to suture the uterus, or techniques of suture closure (continuous suture versus interrupted suture; locking versus unlocked suture).
While blunt dissection of the uterine incision was associated with a reduction in the mean blood loss at the procedure and the need for blood transfusion, there were no other differences identified in clinical outcomes. The use of an auto‐suture device was associated with a reduction in the mean blood loss at the procedure, but an increase in the duration of the procedure when compared with performing a traditional hysterotomy. Similarly, there were no statistically significant differences identified in the clinical outcomes reported.
Closure of the uterus with chromic catgut was associated with a reduction in blood transfusion and complications requiring re‐laparotomy, however, there was no significant difference in any other clinical outcomes. The only trial making this comparison allowed surgeons to use any suture technique, i.e. continuous, continuous locking and interrupted sutures and this is an important potential confounder for these outcomes.
Although single layer closure of the uterine incision was associated with a reduction in mean blood loss, and duration of the operative procedure, there were no statistically significant differences identified in the risk of febrile morbidity and other clinically relevant outcomes. Most of the studies involved in this comparison were assessing different methods of performing the whole caesarean section operation (for example, a "whole procedure" technique, which includes as one aspect the single layer closure versus another "whole procedure technique" that includes a double layer closure). Different components of these procedures involve variation in the methods used to enter the abdominal cavity, which in turn may influence the extent of blood loss, and duration of the procedure.
Overall completeness and applicability of evidence
Overall, reporting of the prespecified review outcomes was poor, with the majority of trials focusing on estimates of mean blood loss and duration of the operative procedure, rather than measures reflecting health outcomes. For many of the outcomes, reporting was from a single trial, with relatively small combined sample size.
Quality of the evidence
Overall, the methodological quality of the trials was variable, with 12 of the 27 included trials adequately describing the randomisation sequence, with less than half describing adequately methods of allocation concealment, and only six trials indicating blinding of outcome assessors.
Agreements and disagreements with other studies or reviews
The literature describing and assessing caesarean section surgical techniques is broad and in general of low quality, and as such the current review is in general agreement with most other studies and reviews in this area.
'Risk of bias' graph: review authors' judgements about each risk of bias item presented as percentages across all included studies.
'Risk of bias' summary: review authors' judgements about each risk of bias item for each included study.
Comparison 1 Methods of performing the uterine incision: auto stapler versus conventional, Outcome 1 Febrile morbidity.
Comparison 1 Methods of performing the uterine incision: auto stapler versus conventional, Outcome 2 Mean blood loss.
Comparison 1 Methods of performing the uterine incision: auto stapler versus conventional, Outcome 3 Duration of surgery.
Comparison 1 Methods of performing the uterine incision: auto stapler versus conventional, Outcome 4 Duration of postnatal stay.
Comparison 1 Methods of performing the uterine incision: auto stapler versus conventional, Outcome 5 Wound complications.
Comparison 1 Methods of performing the uterine incision: auto stapler versus conventional, Outcome 6 Need for blood transfusion.
Comparison 1 Methods of performing the uterine incision: auto stapler versus conventional, Outcome 7 Endometritis.
Comparison 2 Methods of performing the uterine incision: blunt versus sharp dissection, Outcome 1 Postoperative febrile morbidity (including endometritis).
Comparison 2 Methods of performing the uterine incision: blunt versus sharp dissection, Outcome 2 Mean blood loss.
Comparison 2 Methods of performing the uterine incision: blunt versus sharp dissection, Outcome 3 Need for blood transfusion.
Comparison 2 Methods of performing the uterine incision: blunt versus sharp dissection, Outcome 4 Maternal death or serious morbidity.
Comparison 2 Methods of performing the uterine incision: blunt versus sharp dissection, Outcome 5 Duration of surgery.
Comparison 3 Methods of performing the uterine incision: transverse versus cephalad‐caudad blunt extension, Outcome 1 Mean blood loss.
Comparison 3 Methods of performing the uterine incision: transverse versus cephalad‐caudad blunt extension, Outcome 2 Need for blood transfusion.
Comparison 3 Methods of performing the uterine incision: transverse versus cephalad‐caudad blunt extension, Outcome 3 Duration of surgery.
Comparison 4 Single layer uterine closure versus double layer uterine closure, Outcome 1 Postoperative febrile morbidity (including endometritis).
Comparison 4 Single layer uterine closure versus double layer uterine closure, Outcome 2 Blood loss greater than 500 mL.
Comparison 4 Single layer uterine closure versus double layer uterine closure, Outcome 3 Need for blood transfusion.
Comparison 4 Single layer uterine closure versus double layer uterine closure, Outcome 4 Wound infection.
Comparison 4 Single layer uterine closure versus double layer uterine closure, Outcome 5 Operative procedure on wound.
Comparison 4 Single layer uterine closure versus double layer uterine closure, Outcome 6 Postoperative anaemia.
Comparison 4 Single layer uterine closure versus double layer uterine closure, Outcome 7 Complication of future pregnancy.
Comparison 4 Single layer uterine closure versus double layer uterine closure, Outcome 8 Postoperative pain present.
Comparison 4 Single layer uterine closure versus double layer uterine closure, Outcome 9 Complications post‐op requiring re‐laparotomy.
Comparison 4 Single layer uterine closure versus double layer uterine closure, Outcome 10 Length of hospital stay.
Comparison 4 Single layer uterine closure versus double layer uterine closure, Outcome 11 Death or serious maternal morbidity.
Comparison 4 Single layer uterine closure versus double layer uterine closure, Outcome 12 Maternal readmission.
Comparison 5 Techniques for closing the uterus: chromic catgut versus polygactin‐910, Outcome 1 Postoperative febrile morbidity (including endometritis).
Comparison 5 Techniques for closing the uterus: chromic catgut versus polygactin‐910, Outcome 2 Need for blood transfusion.
Comparison 5 Techniques for closing the uterus: chromic catgut versus polygactin‐910, Outcome 3 Wound infection.
Comparison 5 Techniques for closing the uterus: chromic catgut versus polygactin‐910, Outcome 4 Operative procedure on wound.
Comparison 5 Techniques for closing the uterus: chromic catgut versus polygactin‐910, Outcome 5 Postoperative pain present.
Comparison 5 Techniques for closing the uterus: chromic catgut versus polygactin‐910, Outcome 6 Complications post‐op requiring re‐laparotomy.
Comparison 5 Techniques for closing the uterus: chromic catgut versus polygactin‐910, Outcome 7 Death or serious maternal morbidity.
Comparison 5 Techniques for closing the uterus: chromic catgut versus polygactin‐910, Outcome 8 Maternal readmission.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
| 1 Febrile morbidity Show forest plot | 2 | 300 | Risk Ratio (M‐H, Fixed, 95% CI) | 0.92 [0.38, 2.20] |
| 2 Mean blood loss Show forest plot | 1 | 200 | Mean Difference (IV, Fixed, 95% CI) | ‐87.0 [‐175.09, 1.09] |
| 3 Duration of surgery Show forest plot | 1 | 197 | Mean Difference (IV, Fixed, 95% CI) | 3.30 [‐0.02, 6.62] |
| 4 Duration of postnatal stay Show forest plot | 1 | 200 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [‐0.28, 0.28] |
| 5 Wound complications Show forest plot | 1 | 100 | Risk Ratio (M‐H, Fixed, 95% CI) | 1.5 [0.67, 3.35] |
| 6 Need for blood transfusion Show forest plot | 1 | 100 | Risk Ratio (M‐H, Fixed, 95% CI) | 1.5 [0.26, 8.60] |
| 7 Endometritis Show forest plot | 1 | 100 | Risk Ratio (M‐H, Fixed, 95% CI) | 0.2 [0.02, 1.65] |
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
| 1 Postoperative febrile morbidity (including endometritis) Show forest plot | 4 | 1941 | Risk Ratio (M‐H, Fixed, 95% CI) | 0.86 [0.70, 1.05] |
| 2 Mean blood loss Show forest plot | 2 | 1145 | Mean Difference (IV, Random, 95% CI) | ‐53.00 [‐79.48, ‐30.52] |
| 3 Need for blood transfusion Show forest plot | 2 | 1345 | Risk Ratio (M‐H, Fixed, 95% CI) | 0.24 [0.09, 0.62] |
| 4 Maternal death or serious morbidity Show forest plot | 1 | 400 | Risk Ratio (M‐H, Fixed, 95% CI) | 3.0 [0.12, 73.20] |
| 5 Duration of surgery Show forest plot | 1 | 200 | Mean Difference (IV, Fixed, 95% CI) | ‐2.80 [‐5.84, 0.24] |
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
| 1 Mean blood loss Show forest plot | 1 | 811 | Mean Difference (IV, Fixed, 95% CI) | 42.0 [1.31, 82.69] |
| 2 Need for blood transfusion Show forest plot | 1 | 811 | Risk Ratio (M‐H, Fixed, 95% CI) | 1.00 [0.20, 4.91] |
| 3 Duration of surgery Show forest plot | 1 | 811 | Mean Difference (IV, Fixed, 95% CI) | ‐1.50 [‐3.13, 0.13] |
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
| 1 Postoperative febrile morbidity (including endometritis) Show forest plot | 9 | 13890 | Risk Ratio (M‐H, Fixed, 95% CI) | 0.98 [0.85, 1.12] |
| 2 Blood loss greater than 500 mL Show forest plot | 1 | 339 | Risk Ratio (M‐H, Fixed, 95% CI) | 0.70 [0.42, 1.18] |
| 3 Need for blood transfusion Show forest plot | 4 | 13571 | Risk Ratio (M‐H, Random, 95% CI) | 0.86 [0.63, 1.17] |
| 4 Wound infection Show forest plot | 5 | 13389 | Risk Ratio (M‐H, Fixed, 95% CI) | 0.99 [0.89, 1.10] |
| 5 Operative procedure on wound Show forest plot | 3 | 12604 | Risk Ratio (M‐H, Fixed, 95% CI) | 0.80 [0.53, 1.21] |
| 6 Postoperative anaemia Show forest plot | 2 | 1245 | Risk Ratio (M‐H, Fixed, 95% CI) | 1.05 [0.83, 1.32] |
| 7 Complication of future pregnancy Show forest plot | 1 | 145 | Risk Ratio (M‐H, Fixed, 95% CI) | 3.21 [0.13, 77.55] |
| 8 Postoperative pain present Show forest plot | 2 | 9444 | Risk Ratio (M‐H, Random, 95% CI) | 0.88 [0.54, 1.42] |
| 9 Complications post‐op requiring re‐laparotomy Show forest plot | 1 | 9286 | Risk Ratio (M‐H, Fixed, 95% CI) | 0.85 [0.63, 1.16] |
| 10 Length of hospital stay Show forest plot | 1 | 158 | Mean Difference (IV, Fixed, 95% CI) | ‐0.10 [‐0.52, 0.32] |
| 11 Death or serious maternal morbidity Show forest plot | 3 | 12665 | Risk Ratio (M‐H, Fixed, 95% CI) | 1.04 [0.71, 1.54] |
| 12 Maternal readmission Show forest plot | 1 | 9286 | Risk Ratio (M‐H, Fixed, 95% CI) | 1.12 [0.70, 1.79] |
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
| 1 Postoperative febrile morbidity (including endometritis) Show forest plot | 1 | 9544 | Risk Ratio (M‐H, Fixed, 95% CI) | 0.70 [0.49, 1.00] |
| 2 Need for blood transfusion Show forest plot | 1 | 9544 | Risk Ratio (M‐H, Fixed, 95% CI) | 0.49 [0.32, 0.76] |
| 3 Wound infection Show forest plot | 1 | 9544 | Risk Ratio (M‐H, Fixed, 95% CI) | 0.99 [0.82, 1.19] |
| 4 Operative procedure on wound Show forest plot | 1 | 9544 | Risk Ratio (M‐H, Fixed, 95% CI) | 0.64 [0.36, 1.13] |
| 5 Postoperative pain present Show forest plot | 1 | 9544 | Risk Ratio (M‐H, Fixed, 95% CI) | 0.86 [0.70, 1.07] |
| 6 Complications post‐op requiring re‐laparotomy Show forest plot | 1 | 9544 | Risk Ratio (M‐H, Fixed, 95% CI) | 0.58 [0.37, 0.89] |
| 7 Death or serious maternal morbidity Show forest plot | 1 | 9544 | Risk Ratio (M‐H, Fixed, 95% CI) | 0.68 [0.44, 1.06] |
| 8 Maternal readmission Show forest plot | 1 | 9544 | Risk Ratio (M‐H, Fixed, 95% CI) | 1.00 [0.58, 1.72] |
