Diabetes in Pregnancy

Gestational Diabetes (Diagnosis in pregnancy)


  • Results from insulin-antagonistic effects of placental hormones (e.g. human placental lactogen) and steroid hormones, accompanied by an inability of the mother to compensate by increasing insulin production


  • Commonly diagnosed at 28 weeks by routine glucose tolerance test
    • An abnormal fasting glucose but normal 2hr post-prandial glucose may be managed with diet alone (Type A1)
    • If both GTT and 2hr post prandial glucose are high, pharmacological intervention is more likely (Type A2)
    • Will be screened if she is deemed to be at risk:

Risk factors

  • High BM at booking/antenatal visits/28 weeks
  • Family history of DM (gestational or otherwise); previous macrosomic (large) pregnancy; Previous still birth; recurrent glycosuria (at baseline/antenatal visits); obesity; past history of GDM; large for dates uterus


  • All relate to poor bloog glucose control:
    • Pre-eclampsia
    • Polyhydramnios
    • Macrosomia
    • Shoulder dystocia
    • Neonatal hypoglycaemia/hyperbilirubinaemia (jaundice)


  • Diet (first line)- aim for BM between 4-6mmol/l
  • If >=7mmol/l
    • Metformin or insulin
  • Monitor the pregnancy closely
    • Scan at 18 weeks to check growth
    • Eye checks on mother

Pre-existing diabetes mellitus

Control of blood glucose (ideally between 4 and 6 mmol/l) is crucial.  Those with a high HbA1c (>10) should be strongly recommended to avoid pregnancy.

Folic acid supplements are crucial (although this should occur in every planned pregnancy).  Routine diabetic screening (retinopathy in particular) should also be offered.

Pre-existing diabetes carries the same risks as GDM.

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