Routine ultrasound in late pregnancy (after 24 weeks' gestation)
Abstract
Background
Diagnostic ultrasound is used selectively in late pregnancy where there are specific clinical indications. However, the value of routine late pregnancy ultrasound screening in unselected populations is controversial. The rationale for such screening would be the detection of clinical conditions which place the fetus or mother at high risk, which would not necessarily have been detected by other means such as clinical examination, and for which subsequent management would improve perinatal outcome.
Objectives
To assess the effects on obstetric practice and pregnancy outcome of routine late pregnancy ultrasound, defined as greater than 24 weeks' gestation, in women with either unselected or low‐risk pregnancies.
Search methods
We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (February 2008).
Selection criteria
All acceptably controlled trials of routine ultrasound in late pregnancy (defined as after 24 weeks).
Data collection and analysis
All three review authors were involved in assessing trial quality and data extraction.
Main results
Eight trials recruiting 27,024 women were included. The quality of trials overall was satisfactory. There was no difference in antenatal, obstetric and neonatal intervention or morbidity in screened versus control groups. There was a slightly higher caesarean section rate in the screened group, but this difference did not reach statistical significance. Routine late pregnancy ultrasound was not associated with improvements in overall perinatal mortality. Placental grading as an adjunct to third trimester examination scan was associated with a significant reduction in the stillbirth rate in the one trial that assessed it. There is little information on long‐term substantive outcomes such as neurodevelopment. There is a lack of data on maternal psychological effects.
Authors' conclusions
Based on existing evidence, routine late pregnancy ultrasound in low‐risk or unselected populations does not confer benefit on mother or baby. It may be associated with a small increase in caesarean section rates. There is a lack of data about the potential psychological effects of routine ultrasound in late pregnancy, and limited data about its effects on both short‐ and long‐term neonatal and childhood outcome. Placental grading in the third trimester may be valuable, but whether reported results are reproducible remains to be seen, and future research of late pregnancy ultrasound should include evaluation of placental textural assessment.
PICOs
Plain language summary
Routine ultrasound in late pregnancy (after 24 weeks' gestation)
Ultrasound can be used in late pregnancy to assess the baby's condition when there are complications, but carrying out scans on all women is controversial. Scans can be used in late pregnancy to detect problems which may not otherwise be apparent, such as abnormalities in the placenta, in the fluid surrounding the baby, or in the baby's growth. If such problems are identified this may lead to changes in care and improved outcome for babies. At the same time, screening all women may mean that interventions are increased without benefit to mothers or babies. Scans are popular, but women may not fully understand the purpose of their scan and may be either falsely reassured or unprepared for adverse findings. Based on existing evidence, routine ultrasound, after 24 weeks gestation, in low‐risk or unselected women does not provide any benefit for mother or baby. Eight studies that randomised 27,024 women to screening or a control group (no or selective ultrasound, or ultrasound with concealed results) contributed to the review. The quality of trials was satisfactory. There were no differences between groups in the rates of women having additional scans, antenatal admissions, preterm delivery, induction of labour, or instrumental deliveries although the rate of caesarean section increased slightly with screening. For babies, birthweight, condition at birth, interventions such as resuscitation, and admission to special care were similar between groups. Infant survival, with or without congenital abnormalities, was no different with and without routine screening, and childhood development at eight to nine years was similar in the three trials that measured it. None of the trials reported on psychological effects for mothers of routine ultrasound in late pregnancy.
