Ketones or very high glucose in pregnancy: urgent obstetric and diabetes review. DKA occurs at lower glucose levels and more quickly in pregnancy and is a risk to the fetus.
Screening (OGTT)
- Offer an OGTT at 24 to 28 weeks if risk factors are present
- Risk factors: BMI over 30, previous GDM, previous macrosomic baby, first-degree family history, high-risk ethnicity
- Previous GDM: OGTT early (soon after booking) and again at 24 to 28 weeks if normal
- Diagnose if fasting 5.6 mmol/L or more, or 2 h 7.8 mmol/L or more
Capillary glucose targets
- Fasting below 5.3 mmol/L
- 1 h after meals below 7.8 mmol/L (or 2 h below 6.4 mmol/L)
- Keep above 4 mmol/L to avoid hypoglycaemia if on insulin or a sulfonylurea
At target
- Fasting under 5.3, 1 h under 7.8
- Diet and exercise
- Monitor glucose
Above target
- Add metformin
- Then insulin if needed
- Review growth scans
Poor control / macrosomia
- Persistent highs, large for dates
- Insulin, specialist input
- Plan timing and mode of birth
Care plan
1
1. Lifestyle
Dietitian input, diet and exercise advice, and home capillary glucose monitoring.
Dietitian input, diet and exercise advice, and home capillary glucose monitoring.
↓
2
2. Metformin
Add if targets are not met within 1 to 2 weeks of lifestyle change, or if fasting glucose is high at diagnosis.
Add if targets are not met within 1 to 2 weeks of lifestyle change, or if fasting glucose is high at diagnosis.
↓
3
3. Insulin
Add or switch to insulin if targets are still not met, or offer immediately if fasting glucose is 7 mmol/L or more at diagnosis (consider with complications at 6 to 6.9).
Add or switch to insulin if targets are still not met, or offer immediately if fasting glucose is 7 mmol/L or more at diagnosis (consider with complications at 6 to 6.9).
↓
4
4. Delivery and after
Monitor fetal growth; plan timing of birth (usually by 40 to 41 weeks, earlier if complications). Stop GDM treatment after birth; offer a fasting glucose or HbA1c at 6 to 13 weeks and annual review (lifelong type 2 diabetes risk).
Monitor fetal growth; plan timing of birth (usually by 40 to 41 weeks, earlier if complications). Stop GDM treatment after birth; offer a fasting glucose or HbA1c at 6 to 13 weeks and annual review (lifelong type 2 diabetes risk).
Why it matters
- Macrosomia, shoulder dystocia, birth trauma
- Neonatal hypoglycaemia, polyhydramnios
- Pre-eclampsia and higher caesarean rate
Pitfalls
- Not rescreening a woman with previous GDM
- Delaying insulin when fasting glucose is high
- Allowing hypoglycaemia on treatment
- Forgetting postnatal glucose testing and follow-up
MedPrep - www.medprep.uk - Educational revision aid only. Not clinical guidance. Doses are adult examples; check the BNF, current guidelines and local policy, and seek senior advice. Nov 2026