Dr Mary Pierce and Dr Stephanie Baldeweg’s tips on spotting, treating and following-up women who develop diabetes during pregnancy
1 Gestational diabetes is defined as any glucose intolerance first recognised during pregnancy. This is regardless of type of treatment or whether the condition persists after pregnancy. It affects 1-14% of pregnancies – depending on the background population.
2 Maternal risks of gestational diabetes include pre-eclampsia, hypertension, an increased risk of caesarean section and birth trauma. Recurrent gestational diabetes is another risk and, long term, the risk of diabetes and cardiovascular disease is increased.
3 Foetal risks include macrosomia, birth trauma, shoulder dystocia, neonatal hypoglycaemia and respiratory distress syndrome. Obesity and type 2 diabetes in later life are the other risks.
4 Women with risk factors should be encouraged to book for their pregnancy early and the obstetric team should be alerted.
Risk factors for gestational diabetes are:
• obesity (BMI more than 30kg/m2)
• family history of diabetes (first-degree relative)
• personal history of gestational diabetes
• history of diabetes in first-degree relative
• belonging to an ethnic group with a high prevalence of diabetes – South Asian (from India, Pakistan or Bangladesh), black Caribbean or Middle Eastern (Saudi Arabia, UAE, Iraq, Syria, Jordan, Oman, Qatar, Kuwait, Lebanon or Egypt).
• history of large-for-gestational-age baby (more than 4.5kg).
5 Be aware of the type of screening used locally.
Hospitals vary in their type of screening (universal or selective), the tests used for screening (fasting or random blood glucose, oral glucose challenge or oral glucose tolerance test) and the timing of those tests (at booking or 22-28 weeks gestation).
6 Women with a diagnosis of gestational diabetes should have consultant-led care in a multidisciplinary clinic involving a diabetologist as well as an obstetrician.
Women will get dietary and exercise advice and will be taught home blood-glucose monitoring. They should monitor their blood glucose at least five times a day – fasting and one hour postprandial as well as before bed – and if they are unwell. Blood glucose goals are fasting blood glucose of less than 5.5mmol/l and one-hour postprandial blood glucose of less than 7.5mmol/l.
7 Gestational diabetes requires diet modification and possibly treatment with oral hypoglycaemics (metformin) or insulin.
About 20-40% of women will require medical treatment in addition to diet and exercise. However, following recent NICE guidance, metformin may soon become a widely acceptable alternative to insulin in this group.1
8 A long-acting insulin, Insulatard, once or twice daily is used to treat fasting hyperglycaemia.
Postprandial hyperglycaemia requires a short-acting insulin such as Novorapid. Insulin requirements increase with the duration of pregnancy and the doses need titrating up.
9 Treatment of gestational diabetes works.
A recent systematic review and meta-analysis in the BMJ showed that treatment significantly reduced combined end points (any of perinatal death, shoulder dystocia, bone fracture or nerve palsy) and birth trauma (fetal and maternal); in addition one randomised controlled trial suggested a reduction in pre-eclampsia.2 The risk of a large-for-gestational-age baby is the outcome most affected, with treatment reducing the risk by more than 50%.
10 Gestational diabetes increases the risk of subsequent development of type 2 diabetes.
The estimated risk varies hugely between 2% and 70% depending on the population studies. NICE recommends a fasting plasma-glucose test six weeks post-partum and in those not diabetic at six weeks another fasting blood glucose at one year and then annually thereafter. Women should also be tested if they develop symptoms suggestive of type 2 diabetes.
Dr Mary Pierce is a GP in Blackheath, south London
Dr Stephanie Baldeweg is consultant physician in diabetes and endocrinology at University College London Hospital NHS Foundation Trust
Competing interests: none declared
Women with GDM need to test their blood glucose at least five times a day Women with GDM need to test their blood glucose at least five times a day