Gestational Diabetes
High blood glucose first recognised in pregnancy — well-controlled, outcomes are excellent.
Overview
Gestational diabetes (GDM) affects up to 1 in 6 UK pregnancies. It usually develops in the second/third trimester due to placental hormone-induced insulin resistance. Tight glycaemic control reduces macrosomia, shoulder dystocia, pre-eclampsia and neonatal hypoglycaemia. Women with GDM have a 50% lifetime risk of type 2 diabetes.
Symptoms
- • Usually asymptomatic — detected on screening
- • Polyuria, polydipsia, fatigue (uncommon)
- • Macrosomia or polyhydramnios on antenatal scan
- • Recurrent thrush or UTI
Risk factors
- • BMI ≥30
- • Previous baby ≥4.5 kg or previous GDM
- • Family history of diabetes (first-degree)
- • South Asian, Middle Eastern, African–Caribbean ethnicity
- • Age >40, PCOS
Causes
- • Pregnancy hormones (cortisol, placental lactogen, progesterone) cause insulin resistance
- • Pre-existing insulin resistance or beta-cell limitation unmasked
🚨 Red flags — seek urgent care
- • Severe hyperglycaemia or ketonuria — exclude type 1/DKA
- • Reduced fetal movements
- • Pre-eclampsia features (headache, oedema, hypertension)
When to seek care
- • All women with risk factors should be offered a 75 g OGTT at 24–28 weeks
- • Previous GDM: early self-monitoring or OGTT at booking
- • Reduced fetal movements at any time — same-day assessment
Diagnosis
- • 75 g oral glucose tolerance test (OGTT)
- • NICE thresholds: fasting ≥5.6 mmol/L or 2-hour ≥7.8 mmol/L
- • HbA1c not used for diagnosis in pregnancy
- • Exclude pre-existing diabetes (HbA1c at booking in high-risk women)
Treatment
- • Lifestyle: low-glycaemic-index diet, regular activity (30 min daily), weight management
- • Self-monitoring 4× daily; targets: fasting <5.3, 1-hour postprandial <7.8, 2-hour <6.4 mmol/L
- • Metformin if targets not met after 1–2 weeks of lifestyle
- • Insulin (basal ± rapid-acting) if metformin insufficient or fasting glucose ≥7 mmol/L at diagnosis
- • Serial growth scans, increased antenatal surveillance
- • Plan delivery by 40+6 weeks (earlier if complications)
Prevention
- • Pre-pregnancy weight optimisation
- • Regular physical activity during pregnancy
- • Mediterranean-style diet
- • Postnatal follow-up: fasting glucose/HbA1c at 6–13 weeks, then annually
Complications
- • Macrosomia, shoulder dystocia, birth trauma
- • Pre-eclampsia, polyhydramnios, preterm birth
- • Neonatal hypoglycaemia, jaundice, respiratory distress
- • Long-term: maternal type 2 diabetes (50% within 10 years), childhood obesity
Prognosis
With well-controlled glucose, perinatal outcomes are excellent. Glucose usually normalises postpartum, but lifelong follow-up matters because of high T2DM risk.
Education & self-care
Tight glucose control, regular monitoring and active antenatal surveillance keep mother and baby safe. Postnatal lifestyle and annual checks reduce future diabetes risk.
Frequently asked questions
Will I be diabetic forever?
Usually no — but you have a high lifetime risk of type 2 diabetes. Annual screening is important.
Can I avoid insulin?
Often yes, with diet and metformin. Insulin is safe and used when needed to protect mother and baby.
Will my baby be diabetic?
Babies of GDM mothers have a higher long-term risk of obesity and diabetes — healthy lifestyle from the start matters.