Gestational diabetes means diabetes diagnosed for the first time in pregnancy and resolving after delivery. It affects about 10% of women. It is increasing in prevalence, probably due to the increase in obesity and older age of pregnant women. Screening for gestational diabetes is recommended for women based on risk factors. Risk factors for GDM include a first-degree family relative with diabetes, BMI >29.9kg/m2, maternal age >39 years, previous stillbirth, previous macrosomic baby (>4.5kg), macrosomia or polyhydramnios in the current pregnancy, glycosuria in the current pregnancy, polycystic ovarian syndrome and asian ethnicity. The screening test is a 75g oral glucose tolerance test between 24 and 28 weeks gestation. You will be given an appointment to attend for the test. You need to fast from midnight the night before (this includes no chewing gum and no smoking). You have 3 blood tests taken, one fasting and then at 1 and 2 hours after a glucose drink. The results are usually available the same day. You are diab=gnosed with gestational diabetes if your fasting blood glucose is >5.1mmol/L, 1 hour blood glucose is>10.0mmmol/L and 2 hour blood glucose is >8.5mmmol/L.
If you are diagnosed with gestational diabetes you will be referred for diet and exercise advice to keep your blood sugars in the normal range (<5 before eating and <7 after eating). It is important to do this to reduce your risk of pregnancy complications for you and your baby. Most women who do this will have an uncomplicated pregnancy and delivery of a healthy baby.
For women who have high blood sugars or a large baby, despite diet and exercise, medication in pregnancy including metformin and insulin is used. If this is needed you will be transferred to a dedicated diabetic clinic. This clinic includes visits with an endocrinologist (diabetic specialtist).
Ultrasound measurement of fetal weight should take place at least once in the third trimester to make sure you baby is not bigger than it should be. For those with good blood sugar control it is appropriate to await spontaneous labour and aim for a vaginal delivery. Induction of labour is indicated for if your baby is macrosomic (bigger than expected). Your blood glucose levels will be monitored in labour aiming for 4-7mmol/L. If you are taking insulin, intravenous fluids, an insulin regime and supplemental sliding scale of insulin should be prescribed by the team endocrinologist.
After the third stage of labour (delivery of the placenta) your blood glucose levels should return to normal and you can stop medication if you have been taking it for your gestational diabetes. Breastfeeding is encouraged to prevent your baby’s blood sugar going low. Breastfeeding has also been shown to reduce the risk of obesity and type 2 diabetes for the mothers. You will have a repeat 75g oral glucose tolerance test at 6 weeks postpartum. If this is normal then type 2 diabetes is excluded. However, you still have a 50% chance of developing type 2 diabetes within 10 years. So maintaining normal weight and continuing a healthy diet and exercise regime is important.