Techniques of monitoring blood glucose during pregnancy for women with pre‐existing diabetes
Abstract
Background
Self‐monitoring of blood glucose (SMBG) is recommended as a key component of the management plan for diabetes therapy during pregnancy. No existing systematic reviews consider the benefits/effectiveness of various techniques of blood glucose monitoring on maternal and infant outcomes among pregnant women with pre‐existing diabetes. The effectiveness of the various monitoring techniques is unclear.
Objectives
To compare techniques of blood glucose monitoring and their impact on maternal and infant outcomes among pregnant women with pre‐existing diabetes.
Search methods
We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 November 2016), searched reference lists of retrieved studies and contacted trial authors.
Selection criteria
Randomised controlled trials (RCTs) and quasi‐RCTs comparing techniques of blood glucose monitoring including SMBG, continuous glucose monitoring (CGM) or clinic monitoring among pregnant women with pre‐existing diabetes mellitus (type 1 or type 2). Trials investigating timing and frequency of monitoring were also included. RCTs using a cluster‐randomised design were eligible for inclusion but none were identified.
Data collection and analysis
Two review authors independently assessed study eligibility, extracted data and assessed the risk of bias of included studies. Data were checked for accuracy. The quality of the evidence was assessed using the GRADE approach.
Main results
This review update includes at total of 10 trials (538) women (468 women with type 1 diabetes and 70 women with type 2 diabetes). The trials took place in Europe and the USA. Five of the 10 included studies were at moderate risk of bias, four studies were at low to moderate risk of bias, and one study was at high risk of bias. The trials are too small to show differences in important outcomes such as macrosomia, preterm birth, miscarriage or death of baby. Almost all the reported GRADE outcomes were assessed as being very low‐quality evidence. This was due to design limitations in the studies, wide confidence intervals, small sample sizes, and few events. In addition, there was high heterogeneity for some outcomes.
Various methods of glucose monitoring were compared in the trials. Neither pooled analyses nor individual trial analyses showed any clear advantages of one monitoring technique over another for primary and secondary outcomes. Many important outcomes were not reported.
1. Self‐monitoring versus standard care (two studies, 43 women): there was no clear difference for caesarean section (risk ratio (RR) 0.78, 95% confidence interval (CI) 0.40 to 1.49; one study, 28 women) or glycaemic control (both very low‐quality), and not enough evidence to assess perinatal mortality and neonatal mortality and morbidity composite. Hypertensive disorders of pregnancy, large‐for‐gestational age, neurosensory disability, and preterm birth were not reported in either study.
2. Self‐monitoring versus hospitalisation (one study, 100 women): there was no clear difference for hypertensive disorders of pregnancy (pre‐eclampsia and hypertension) (RR 4.26, 95% CI 0.52 to 35.16; very low‐quality: RR 0.43, 95% CI 0.08 to 2.22; very low‐quality). There was no clear difference in caesarean section or preterm birth less than 37 weeks' gestation (both very low quality), and the sample size was too small to assess perinatal mortality (very low‐quality). Large‐for‐gestational age, mortality or morbidity composite, neurosensory disability and preterm birth less than 34 weeks were not reported.
3. Pre‐prandial versus post‐prandial glucose monitoring (one study, 61 women): there was no clear difference between groups for caesarean section (RR 1.45, 95% CI 0.92 to 2.28; very low‐quality), large‐for‐gestational age (RR 1.16, 95% CI 0.73 to 1.85; very low‐quality) or glycaemic control (very low‐quality). The results for hypertensive disorders of pregnancy: pre‐eclampsia and perinatal mortality are not meaningful because these outcomes were too rare to show differences in a small sample (all very low‐quality). The study did not report the outcomes mortality or morbidity composite, neurosensory disability or preterm birth.
4. Automated telemedicine monitoring versus conventional system (three studies, 84 women): there was no clear difference for caesarean section (RR 0.96, 95% CI 0.62 to 1.48; one study, 32 women; very low‐quality), and mortality or morbidity composite in the one study that reported these outcomes. There were no clear differences for glycaemic control (very low‐quality). No studies reported hypertensive disorders of pregnancy, large‐for‐gestational age, perinatal mortality (stillbirth and neonatal mortality), neurosensory disability or preterm birth.
5.CGM versus intermittent monitoring (two studies, 225 women): there was no clear difference for pre‐eclampsia (RR 1.37, 95% CI 0.52 to 3.59; low‐quality), caesarean section (average RR 1.00, 95% CI 0.65 to 1.54; I² = 62%; very low‐quality) and large‐for‐gestational age (average RR 0.89, 95% CI 0.41 to 1.92; I² = 82%; very low‐quality). Glycaemic control indicated by mean maternal HbA1c was lower for women in the continuous monitoring group (mean difference (MD) ‐0.60 %, 95% CI ‐0.91 to ‐0.29; one study, 71 women; moderate‐quality). There was not enough evidence to assess perinatal mortality and there were no clear differences for preterm birth less than 37 weeks' gestation (low‐quality). Mortality or morbidity composite, neurosensory disability and preterm birth less than 34 weeks were not reported.
6. Constant CGM versus intermittent CGM (one study, 25 women): there was no clear difference between groups for caesarean section (RR 0.77, 95% CI 0.33 to 1.79; very low‐quality), glycaemic control (mean blood glucose in the 3rd trimester) (MD ‐0.14 mmol/L, 95% CI ‐2.00 to 1.72; very low‐quality) or preterm birth less than 37 weeks' gestation (RR 1.08, 95% CI 0.08 to 15.46; very low‐quality). Other primary (hypertensive disorders of pregnancy, large‐for‐gestational age, perinatal mortality (stillbirth and neonatal mortality), mortality or morbidity composite, and neurosensory disability) or GRADE outcomes (preterm birth less than 34 weeks' gestation) were not reported.
Authors' conclusions
This review found no evidence that any glucose monitoring technique is superior to any other technique among pregnant women with pre‐existing type 1 or type 2 diabetes. The evidence base for the effectiveness of monitoring techniques is weak and additional evidence from large well‐designed randomised trials is required to inform choices of glucose monitoring techniques.
PICOs
Plain language summary
Methods for monitoring blood glucose in pregnant women with diabetes to improve outcomes
What is the issue?
If a mother already has diabetes when she becomes pregnant, she and her baby are at a higher risk of various problems in pregnancy, labour, birth and later. During pregnancy, the mother will have her blood glucose levels (sometimes referred to as blood sugar levels) monitored so appropriate steps can be taken to control her blood glucose. This Cochrane review looked for the best test for measuring blood glucose during pregnancy in order to control blood glucose levels and so reduce problems for babies and mothers. We collected and analysed all relevant studies to answer this question (search date: November 2016).
Why is this important?
Diabetes can cause problems for pregnant women and their babies, including early births, large babies, difficult births and the need for caesarean section. The problems also include a risk to the baby of bleeding in the brain (intracranial haemorrhage), and during labour, there is an increased risk of the baby’s shoulder becoming stuck (shoulder dystocia). After the birth, there is an increased risk of low blood sugar (hypoglycaemia), jaundice and breathing problems. The babies are more likely to be admitted to an intensive care unit. Later, there is an increased risk of the baby developing diabetes as a child.
Women with existing diabetes that is not well‐controlled at the time of conception and in the first three months of pregnancy are at increased risk of miscarriage, of having a baby with developmental problems or stillbirth. Several methods for monitoring blood glucose levels are used including regular testing at antenatal clinics, self‐monitoring, or the use of special equipment that can continuously monitor glucose levels during pregnancy. A more accurate measure of blood sugar may lead to more effective control of blood glucose and a reduction in the potential problems for babies and mothers.
What evidence did we find?
We found 10 trials involving 538 women and babies. We found studies that compared various methods of glucose monitoring: self‐monitoring versus standard care, self‐monitoring versus hospitalisation, monitoring before meals versus monitoring after meals, glucose monitoring, automated monitoring versus conventional system, continuous glucose monitoring (CGM) versus intermittent monitoring and constant CGM versus intermittent CGM. The trials were from European countries and the USA. They looked at different techniques of monitoring and reported on different outcomes. The number of women in each study was generally small. The evidence was mostly of very low‐quality, so we cannot be certain of the results.
The results did not show that any one monitoring technique was better than others. There was no clear difference between the monitoring techniques when mothers’ control of blood glucose or high blood pressure disorders were looked at. Similarly, we found no difference in rates of caesarean section, the number of large babies, the number of babies who died or had serious health problems, or the number of babies being born too early (preterm). We do not know if this is because there is no difference between the techniques, or if there is a difference that these studies did not manage to show.
What does this mean?
The review showed that there is not enough evidence to say with any certainty which monitoring method for blood glucose is best. More research is needed to find out which monitoring method, if any, is best at reducing the risk of complications.
