Gestational diabetes

Diabetes mellitus may be a pre-existing problem or develop during pregnancy, gestational diabetes. It complicates up to 1 in 20 pregnancies. NICE estimate the following breakdown:

• 87.5% have gestational diabetes
• 7.5% have type 1 diabetes
• 5% have type 2 diabetes

Gestational diabetes is the second most common medical disorder complicating pregnancy (after hypertension), affecting around 4% of pregnancies.

Risk factors

• BMI of > 30 kg/m²
• previous macrosomic baby weighing 4.5 kg or above
• previous gestational diabetes
• first-degree relative with diabetes
• family origin with a high prevalence of diabetes (South Asian, black Caribbean and Middle Eastern)

Diagnosis

Screening for gestational diabetes

• women who've previously had gestational diabetes: oral glucose tolerance test (OGTT) should be performed as soon as possible after booking and at 24-28 weeks if the first test is normal. NICE also recommend that early self-monitoring of blood glucose is an alternative to the OGTTs
• women with any of the other risk factors should be offered an OGTT at 24-28 weeks

Diagnostic thresholds for gestational diabetes

• these have recently been updated by NICE, gestational diabetes is diagnosed if either:
  • fasting glucose is >= 5.6 mmol/L
  • 2-hour glucose is >= 7.8 mmol/L