A complete guide to GDM — what it means, how to manage it, and how to protect your baby
Gestational diabetes is one of the most common pregnancy complications — and it is not caused by anything you did.
High blood sugar that develops during pregnancy — usually between 24 and 28 weeks — because pregnancy hormones block insulin from working normally.
Family history of diabetes (parent or sibling)
Prior pregnancy with GDM
Prior large baby (>9 lbs / 4,000 g)
Polycystic ovary syndrome (PCOS)
BMI ≥25 before pregnancy (≥23 in Asian Americans)
Physical inactivity
Age 35 or older
Hypertension or heart disease
Hispanic / Latina
African American
Native American
Asian American
Pacific Islander
Screening typically happens between 24 and 28 weeks using a two-step approach.
Drink a 50g glucose liquid. Blood drawn 1 hour later. No fasting required. If result ≥130–140 mg/dL → proceed to Step 2.
Fasting required. Drink 100g glucose liquid. Blood drawn 4 times: fasting, 1hr, 2hr, and 3hr. GDM diagnosed if 2 or more values are elevated.
| Type | Description | Treatment Plan |
|---|---|---|
| A1GDM Diet-Controlled |
Blood sugar stays in range with healthy eating and activity alone | Medical nutrition therapy + exercise + daily glucose monitoring |
| A2GDM Medication-Controlled |
Blood sugar requires medication to stay consistently in range | All lifestyle changes PLUS insulin or metformin + additional fetal monitoring |
Most accurate — measures glucose directly from blood. Required for all treatment decisions. Test fasting + 1 or 2 hours after each meal.
Reads glucose in interstitial fluid — runs 15–20 min behind actual blood sugar. Great for spotting food trends. Always confirm very low or high readings with a fingerstick.
You don't need to eliminate carbohydrates. The goal is to choose the right type and amount to keep blood sugar stable.
Whole grains (brown rice, quinoa, oats, whole wheat)
Non-starchy vegetables (spinach, broccoli, peppers)
Legumes & beans (lentils, chickpeas, black beans)
Whole fruits in moderation
Healthy proteins & fats (nuts, eggs, avocado, lean meats)
White bread, white rice, regular pasta
Sugary drinks (juice, soda, sweet tea, flavored coffee)
Processed snacks (chips, crackers, granola bars)
Sweets & desserts
Sweetened breakfast foods (sugary cereals, flavored yogurt)
Walking, swimming, and prenatal yoga help muscles use glucose, naturally lowering blood sugar. Aim for 30 minutes most days. Use the Talk Test — you should be able to hold a conversation while exercising. A 10–15 min walk after meals is one of the most effective tools.
Insulin (preferred by ACOG/SMFM) — does NOT cross the placenta, highly effective, precisely dosed.
Metformin — oral pill taken with meals; does cross the placenta but is generally safe; often used when insulin is declined.
We measure the baby's head, belly, and leg bone to estimate weight and check amniotic fluid. Typically around 32 and 36 weeks. Goal: detect macrosomia (large baby) early so we can plan a safe delivery.
NST (Non-Stress Test) — monitors baby's heart rate for 20 min. BPP (Biophysical Profile) — checks movement, breathing, tone, and fluid. Typically starts at 32 weeks, done 1–2× per week for A2GDM.
| GDM Type | Typical Delivery Timing | Notes |
|---|---|---|
| A1GDM Diet-Controlled |
39–40 weeks | Can often wait for labor to start naturally. Delivery by 40w6d recommended. |
| A2GDM Medication-Controlled |
39 weeks | Induction typically scheduled at 39w0d–39w6d. Placenta may age faster. |
| Complications | 37–38 weeks | Poor glucose control, preeclampsia, or fetal growth concerns. |
Improves insulin sensitivity. Supports healthy weight. Breastfeeding ≥3 months can cut your lifetime Type 2 Diabetes risk by up to 50%.
Schedule between 4 and 12 weeks after delivery. Test: 75g 2-Hour Oral GTT (not A1C — inaccurate this soon postpartum). Normal → re-screen every 1–3 years.
50–70% of women with GDM develop Type 2 Diabetes within 10 years. Continue healthy eating, stay active, and maintain a healthy weight. Don't skip follow-up screening.