Gestational Diabetes: Screening, Targets and Risks
Gestational diabetes is high blood sugar that first appears during pregnancy, usually in the second half. It affects roughly 6 to 9 percent of pregnancies in the US, often causes no symptoms, and is found through routine screening. Treated well, most mothers and babies do fine.
Why it happens
Placental hormones make the body more resistant to insulin as pregnancy progresses — a normal change that keeps glucose available for the baby. If the pancreas cannot produce enough extra insulin, blood sugar rises.
Risk factors
- Overweight before pregnancy
- Gestational diabetes in a previous pregnancy, or a previous baby weighing more than 9 lb (4 kg)
- Prediabetes, polycystic ovary syndrome
- Family history of type 2 diabetes
- Age over 35
- Black, Hispanic/Latino, American Indian, Asian American or Pacific Islander background
Screening at 24–28 weeks
Women at high risk are often tested early in pregnancy for undiagnosed diabetes. Everyone else is screened at 24–28 weeks with one of two approaches:
| Approach | Test | Gestational diabetes if |
|---|---|---|
| One-step | 75 g OGTT, fasting | Any one value: fasting ≥ 92 · 1 h ≥ 180 · 2 h ≥ 153 mg/dL |
| Two-step (common in the US) | 1) 50 g glucose drink, non-fasting, 1-hour value 2) if raised: 100 g OGTT, fasting, 3 hours | Step 1: ≥ 130–140 mg/dL → step 2 Step 2: two or more values at or above the cut-offs |
Blood sugar targets in pregnancy
| Measurement | Target |
|---|---|
| Fasting | below 95 mg/dL (5.3 mmol/L) |
| 1 hour after a meal | below 140 mg/dL (7.8 mmol/L) |
| 2 hours after a meal | below 120 mg/dL (6.7 mmol/L) |
Most women test four times a day: fasting and after each main meal.
Treatment
- Nutrition: regular meals and snacks, carbohydrates spread through the day, fiber-rich choices, few sugary drinks — ideally with a dietitian.
- Activity: about 30 minutes most days, for example walking after meals, if your obstetric care team agrees.
- Medication if targets aren't met: insulin is the preferred medicine in pregnancy; metformin or glyburide are used in some cases.
Why treatment matters
Untreated, high maternal glucose makes the baby produce extra insulin and grow large (macrosomia), raising the risk of a difficult birth, cesarean section, low blood sugar in the newborn and later obesity. The mother has a higher risk of preeclampsia. Good control reduces these risks substantially.
After birth
Gestational diabetes usually resolves after delivery, but it signals a much higher lifetime risk of type 2 diabetes — up to around half of women develop it within 10 years. Recommended: a glucose tolerance test 4–12 weeks after birth, then testing at least every 1–3 years. Breastfeeding, regaining a healthy weight and staying active lower the risk. See How to Prevent Type 2 Diabetes.
Sources: ADA: Gestational diabetes · NIDDK: Gestational diabetes · ADA Standards of Care
Check a blood glucose reading
Related guides
- Diabetes: Types, Symptoms, Diagnosis and Treatment
- Type 1 vs. Type 2 Diabetes: The Key Differences
- LADA Diabetes (Type 1.5): Signs, Tests, Treatment
- How to Prevent Type 2 Diabetes
- What Is Normal Blood Sugar? Ranges by Time of Day
- Blood Glucose Levels Chart (mg/dL and mmol/L)
Educational content only; not medical advice. Follow the treatment plan you have agreed with your doctor or diabetes team. In an emergency, call 911 (US) or your local emergency number.