What is the issue?

The aim of this Cochrane overview was to provide a summary of the effects of interventions for women who develop diabetes during pregnancy (gestational diabetes mellitus, GDM) and the effects on women's health and the health of their babies. We assessed all relevant Cochrane Reviews (date of last search: January 2018).

Why is this important?

GDM can occur in mid-to-late pregnancy. High blood glucose levels (hyperglycaemia) possibly have negative effects on both the woman and her baby's health in the short- and long-term.

For women, GDM can mean an increased risk of developing high blood pressure and protein in the urine (pre-eclampsia). Women with GDM also have a higher chance of developing type 2 diabetes, heart disease, and stroke later in life. Babies born to mothers with GDM are at increased risk of being large, having low blood glucose (hypoglycaemia) after birth, and yellowing of the skin and eyes (jaundice). As these babies become children, they are at higher risk of being overweight and developing type 2 diabetes.

Several Cochrane Reviews have assessed different interventions for women with GDM. This overview brings these reviews together. We looked at diet, exercise, drugs, supplements, lifestyle changes, and ways GDM is managed or responded to by the healthcare team.

What evidence did we find?

We found 14 Cochrane systematic reviews and included 10 reviews covering 128 studies in our analysis, which included a total of 17,984 women, and their babies. The quality of the evidence ranged from very low to high.

We looked at:

• Dietary interventions (including change to low or moderate glycaemic index (GI) diet, calorie restrictions, low carbohydrate diet, high complex carbohydrate diet, high saturated fat diet, high fibre diet, soy-protein enriched diet, etc.)

We found there were not enough data on any one dietary intervention to be able to say whether it helped or not.

• Exercise programmes (including brisk walking, cycling, resistance circuit-type training, instruction on active lifestyle, home-based exercise programme, 6-week or 10-week exercise programme, yoga, etc.)

Similarly, there were not enough data on any specific exercise regimen to say if it helped or not.

• Taking insulin or other drugs to control diabetes (including insulin and oral glucose lowering drugs).

Insulin probably increases the risk of high blood pressure and its problems in pregnancy (hypertensive disorders of pregnancy) when compared to oral therapy (moderate-quality evidence).

• Supplements (myo-inositol given as a water-soluble powder or capsule).

We found there was not enough data to be able to say if myo-inositol was helpful or not.

• Lifestyle changes which combine two or more interventions such as: healthy eating, exercise, education, mindfulness eating (focusing the mind on eating), yoga, relaxation, etc.

Lifestyle interventions may be associated with fewer babies being born large (moderate-quality evidence) but may result in an increase in inductions of labour (moderate-quality evidence).

• Management strategies (including early birth, methods of blood glucose monitoring).

We found little data for strategies which included planned induction of labour or planned birth by caesarean section, and there was no clear difference in outcomes among these care plans. Similarly, we found no clear difference among outcomes for different methods of blood glucose monitoring.

What does this mean?

There are limited data on the various interventions. Lifestyle changes (including as a minimum healthy eating, physical activity, and self-monitoring of blood sugar levels) was the only intervention that showed possible health improvements for women and their babies. Lifestyle interventions may result in fewer babies being large. Conversely, in terms of harms, lifestyle interventions may also increase the number of inductions. Taking insulin was also associated with an increase in hypertensive disorders, when compared to oral therapy. There was very limited information on long-term health and health services costs. Women may wish to discuss lifestyle changes around their individual needs with their health professional. Further high-quality research is needed.