Diabetes in pregnancy

Diabetes can be pre-existent or presenting during pregnancy: the latter is called gestational diabetes (GDM).

Gestational diabetes mellitus (GDM) is any degree of impaired glucose tolerance first recognised during pregnancy. Most women with GDM revert to normal glucose metabolism after delivery of their babies; however, they are at risk of developing type 2 diabetes later in life as are their offspring.

Risk factors (and indication for screening)

  • BMI >35 kg/m2
  • Age >40 years
  • GDM in previous pregnancy
  • Family history (8 first degree relatives) of diabetes
  • Previous unexplained third trimester death, macrosomic baby (weight >4 kg)
  • Polyhydramnios
  • Glycosuria
  • Foetus large for gestational age

Diagnostic criteria for gestational diabetes

  • Fasting blood sugar >5.6 mmol/L or
  • Plasma glucose >7.8 mmol/L 2 hours after 75 g glucose tolerance test

Therapeutic targets

  • Pre prandial blood glucose <5.3 mmol/L
  • 1-hour postprandial glucose <7.8 mmol/L
  • 2-hour postprandial glucose <6.4 mmol/L


  • Stop smoking, moderate exercise, dietary advice

If obese and mild diabetes consider

  • Metformin 500 mg (start with one tablet a day, increase by 500 mg per week up to max 2 g per day
    in divided doses)

If not controlled:

  • Insulin
  • Mothers with diabetes should be advised to deliver in hospital

For more on diabetes, visit DIABETES MELLITUS