Interventions before and between pregnancies better for reducing gestational diabetes

• Gestational diabetes mellitus (GDM) continues to increase. One in 6 pregnancies globally is affected by hyperglycaemia, with 84% of these being GDM (IDF, 2017).
• Type 2 diabetes can be prevented, so it should be possible to prevent or reduce GDM. This is important as GDM can result in adverse pregnancy outcomes, neonatal problems and long-term health issues for mother and offspring.
• Pregnancy is an insulin-resistant state, but this is worsened in obesity. GDM is heterogeneous with regard to the time of onset and the underlying pathophysiology, and insulin secretion defects have also been identified in GDM.
• A Cochrane Review summarised the evidence base on interventions to prevent women from developing GDM (Griffith et al, 2020). The studies used different diagnostic thresholds and times of intervention, but the evidence quality was low to moderate.
• Some evidence for combined diet and exercise in reducing gestational weight gain, but not GDM.
• Supplementation with myo-inositol or vitamin D (if deficient) and metformin during pregnancy show limited evidence for reduction in GDM, but the studies are difficult to interpret as the populations were so different, uptake varied, and geography and ethnicity differed.
• Combinations of lifestyle, supplementation and medication or interventions prior to and between pregnancies should be considered. Weight loss, however achieved, is likely to be beneficial.

What else is new?

• A recent meta-analysis suggests an almost 10-fold increased risk of progression to type 2 diabetes in women with a history of GDM, higher than previously identified (Vounzoulaki et al, 2020). Postnatal screening and annual screening thereafter are important.
• HAPO Follow-Up Study (HAPO FUS) confirms higher childhood obesity and adiposity at ages 10–14 years associated with increasing maternal glucose levels during pregnancy.

What might we do differently?

• Ensure that we code those with gestational diabetes, so they can be identified by searches.
• Optimise postnatal testing (fasting blood glucose at 6–13 weeks postnatally or HbA_1c at >13 weeks), with annual screening thereafter.
• If postnatal fasting plasma glucose is 6–6.9 mmol/L or HbA_1c is 39–47 mmol/mol, manage as per non-diabetic hyperglycaemia (e.g. refer to NHS Diabetes Prevention Programme or signpost to lifestyle resources).
• Encourage lifestyle change and weight loss before, between and after pregnancy, and encourage breastfeeding.
• Measure and monitor high-risk children from GDM pregnancies and ensure early interventions if overweight or obesity develop.