What is the issue?

Gestational diabetes mellitus (GDM) is a glucose intolerance leading to high concentrations of glucose (sugar) in the blood (hyperglycaemia) that begins or is first recognised during pregnancy. Monitoring of blood glucose levels is an important way to maintain control of sugar concentrations in the blood. There are several different methods for monitoring blood glucose which can be carried out in different settings (e.g. at home or hospital), however it is not clear which is best for limiting health complications for women and their babies.

Why is this important?

Women with GDM are more likely to develop pre-eclampsia (a dangerous condition characterised by high blood pressure) during pregnancy, and to have the birth induced, suffer trauma to the perineum during birth, or to give birth by caesarean section. Their babies are more likely to be large for their gestational age at birth, develop low blood sugar (hypoglycaemia), and suffer from complications leading to death. Both the women and their babies are more likely to develop long-term health complications, including type 2 diabetes.

What evidence did we find?

We searched the medical literature in September 2016 and included 11 randomised controlled trials (RCTs) involving 1272 women with GDM and their babies. Three trials were supported by commercial partners.

We included five different comparisons:

1) telemedicine (transmission of glucose concentrations from home to healthcare professionals for review) versus standard care (face-to-face review in a clinic/hospital) (five RCTs);

2) self-monitoring of glucose (at home) versus periodic monitoring of glucose (less frequently at face-to-face visits) (two RCTs);

3) use of a continuous glucose monitoring system (CCMS) versus less frequent self-monitoring of glucose (two RCTs);

4) modem technology (transmitting glucose concentrations directly from glucose meters to healthcare professionals) versus telephone transmission of glucose concentrations (one RCT);

5) postprandial (after meal) versus preprandial (before meal) monitoring of glucose (one RCT).

Telemedicine versus standard care for glucose monitoring (five RCTs): there were no clear differences between women in the telemedicine and standard care groups for pre-eclampsia or hypertension, caesarean section or induction of labour; or for their babies being born large-for-gestational age, developing a serious morbidity, or having hypoglycaemia. There were no deaths in the two RCTs that reported on deaths of babies.

Self-monitoring versus periodic glucose monitoring (two RCTs): there were no clear differences between women in the self-monitoring and periodic glucose monitoring groups for pre-eclampsia or caesarean section; or for their babies dying, being born large-for-gestational age, or developing hypoglycaemia.

CGMS versus self-monitoring of glucose (two RCTs): there was no clear difference between women in the CGMS and self-monitoring groups for caesarean section; or for babies being born large-for-gestational age, or developing hypoglycaemia. There were no deaths of babies in the two RCTs.

Modem versus telephone transmission for glucose monitoring (one RCT): this RCT reported none of the outcomes we considered most important.

Postprandial versus preprandial glucose monitoring (one RCT): there were no clear differences between women in the postprandial and preprandial glucose monitoring groups for pre-eclampsia, caesarean section or perineal trauma; or for babies developing hypoglycaemia. Babies born to women in the postprandial glucose monitoring group were less likely to be born large-for-gestational age than babies in the preprandial group.

The quality of the evidence for the above findings was low or very low. None of the 11 RCTs reported on postnatal depression, postnatal weight retention, return to pre-pregnancy weight, or development of type 2 diabetes for the women; or disability, adiposity or development of type 2 diabetes for the babies as children or adults.

What does this mean?

Blood glucose monitoring is an important strategy for managing GDM, however it remains unclear what methods are best. Conclusive evidence from RCTs is not yet available to guide practice, although a range of methods has been investigated. Few RCTs have compared the same or similar interventions, RCTs have been small and have reported limited findings. Further large, well-designed, RCTs are required to assess the effects of different methods and settings for blood glucose monitoring for women with GDM in order to improve outcomes for women and their babies in the short and long term.