FFinalistSouthampton · 2027
Obstetrics & gynaecology
AKT · Obstetrics & gynaecology/Antenatal & medical

Diabetes in pregnancy

Gestational or pre-existing diabetes

Overview

Either gestational diabetes (glucose intolerance first recognised in pregnancy) or pre-existing type 1/2 diabetes. Raises risks of macrosomia, shoulder dystocia, neonatal hypoglycaemia, pre-eclampsia and congenital anomaly (pre-existing).

Recognise

  • Often asymptomatic — detected on screening (OGTT)
  • Risk factors: BMI >30, previous macrosomia/GDM, family history, ethnicity, PCOS
  • Complications: macrosomia, polyhydramnios, shoulder dystocia, neonatal hypoglycaemia

Red flags

  • Poor glycaemic control; pre-existing diabetes with retinopathy/nephropathy; DKA

Differentials & how to tell them apart

Pre-existing undiagnosed type 2 diabeteshigh early HbA1c, persists postpartum
Normal pregnancy glycosurianormal OGTT

Investigations

OGTT (75 g) at 24–28 weeks for risk factors (or earlier if previous GDM). Diagnostic thresholds: fasting ≥5.6 or 2-hour ≥7.8 mmol/L. HbA1c and retinal/renal screening in pre-existing diabetes.

Management

Diet/exercise → metformin → insulin (stepwise to glucose targets)

  1. 1Gestational: trial of diet and exercise first if fasting glucose <7.Gate: If glucose targets not met in 1–2 weeks → metformin; add/switch to insulin if still not met. Fasting ≥7 at diagnosis → start insulin immediately
  2. 2Pre-existing diabetes: optimise control pre-conception, 5 mg folic acid, stop teratogenic drugs (ACEi/statins), aspirin from 12 weeks, retinal/renal screening.
  3. 3Deliver by ~37–39 weeks depending on control; manage neonatal hypoglycaemia. GDM: postpartum OGTT/HbA1c (resolves but recurs).
Diet + exercise — first-line if glucose mildly raised
Metformin — first-line drug if targets not met
Insulin — added/first-line if fasting glucose high (≥7) or complications
Folic acid 5 mg + aspirin — pre-existing: high-dose folate pre-conception; aspirin from 12 weeks

Key points

Macrosomia → shoulder dystocia risk. Neonatal hypoglycaemia after delivery (fetal hyperinsulinaemia). GDM usually resolves postpartum but carries future type 2 risk — screen.

Monitor & prognosis

Glucose diaries, fetal growth (USS), pre-eclampsia; neonatal glucose.

Good with control; GDM resolves but predicts later T2DM.

Source: NICE NG3 (diabetes in pregnancy)