🤰 Gestational Diabetes Overview: Diabetes During Pregnancy Explained

Pregnancy brings many changes to a woman’s body, including how it handles blood sugar. For some women, this leads to gestational diabetes mellitus (GDM) — a temporary form of diabetes that appears during pregnancy and usually resolves after delivery. While it may sound alarming, GDM can be managed successfully. Dr. Ravi Sishir Reddy explains what gestational diabetes is, why it happens, how it is diagnosed, and the steps to protect both mother and baby.

1. What Is Gestational Diabetes?

Gestational diabetes is diabetes that is first diagnosed during pregnancy (typically in the second or third trimester). It occurs because the placenta produces hormones — such as human placental lactogen, estrogen, and progesterone — that make the mother’s cells more resistant to insulin. For most women, the pancreas can compensate by producing extra insulin. But when the pancreas cannot keep up, blood sugar rises, leading to GDM. It affects approximately 7‑15% of pregnancies worldwide, with India having one of the highest rates due to genetic predisposition.

GDM usually resolves within weeks after delivery because the placenta — and its insulin‑blocking hormones — is gone. However, it is a strong predictor of future Type 2 diabetes in both the mother and the child.

2. Who Is at Risk for Gestational Diabetes?

Any pregnant woman can develop GDM, but the risk is higher if you have:

• A family history of diabetes (especially parents or siblings).
• Previous gestational diabetes in a prior pregnancy.
• Overweight or obesity before pregnancy.
• Polycystic ovary syndrome (PCOS).
• Age over 25 (risk increases further after 35).
• South Asian, Middle Eastern, or African ethnicity.
• Previous delivery of a baby weighing more than 4 kg (macrosomia).
• Unexplained stillbirth or congenital anomalies in a prior pregnancy.

Because of the high prevalence, universal screening for GDM is recommended for all pregnant women in India, regardless of risk factors.

3. How Is Gestational Diabetes Diagnosed?

In India, the most common approach is the Oral Glucose Tolerance Test (OGTT) with 75 grams of glucose, performed at 24‑28 weeks of pregnancy. Some centres use the two‑step method (a 50‑gram glucose challenge followed by a full OGTT if positive). The diagnostic thresholds are stricter than for non‑pregnant adults:

• Fasting: ≥ 92 mg/dL (5.1 mmol/L)
• 1‑hour: ≥ 180 mg/dL (10.0 mmol/L)
• 2‑hour: ≥ 153 mg/dL (8.5 mmol/L)

A diagnosis is made if any one of these values meets or exceeds the threshold. Because many Indian women have elevated fasting glucose even in early pregnancy, some guidelines recommend screening at the first antenatal visit, and then repeating at 24‑28 weeks if the initial test was normal.

👉 Read more: Glucose Tolerance Test (OGTT) →

4. What Are the Risks of Untreated GDM?

Uncontrolled gestational diabetes can lead to complications for both the mother and the baby:

• For the baby: Excessive birth weight (macrosomia) leading to difficult delivery and shoulder dystocia; low blood sugar (neonatal hypoglycemia) after birth; respiratory distress syndrome; jaundice; and a higher lifetime risk of obesity and Type 2 diabetes.
• For the mother: High blood pressure and preeclampsia; polyhydramnios (excessive amniotic fluid); preterm birth; increased likelihood of C‑section; and a 50‑70% risk of developing Type 2 diabetes within 5‑10 years after delivery.

The good news: these risks are dramatically reduced when blood sugar is well‑controlled.

5. How Is Gestational Diabetes Managed?

The cornerstone of GDM management is medical nutrition therapy — a carefully planned diet that provides adequate calories and nutrients for the pregnancy while controlling blood sugar. Other strategies include:

• Dietary changes: A registered dietitian can help create a meal plan with controlled carbohydrate portions, spread across three meals and two to three snacks to avoid large glucose spikes. Emphasis is placed on whole grains, vegetables, lean protein, and healthy fats, while limiting sugary foods and refined carbs.
• Regular blood glucose monitoring: Women with GDM are taught to check their blood sugar at home, typically fasting and 1‑2 hours after each meal. Targets: fasting < 95 mg/dL, 1‑hour post‑meal < 140 mg/dL, or 2‑hour post‑meal < 120 mg/dL (these are stricter than for non‑pregnant diabetics).
• Physical activity: Moderate walking or prenatal yoga, if not contraindicated, helps improve insulin sensitivity.
• Medication if needed: If blood sugar remains above target despite diet and exercise, insulin is the first‑line pharmacotherapy. Metformin and glyburide are also used in some contexts but must be prescribed and monitored by a specialist.

6. After Delivery: What Happens Next?

For most women, blood sugar normalises within hours to days after delivery. However, it is essential to retest at 6‑12 weeks postpartum with a 75‑gram OGTT to confirm that diabetes has resolved. Even if the test is normal, women with a history of GDM should be screened for Type 2 diabetes every 1‑3 years for life, as the risk remains elevated.

Dr. Reddy strongly encourages breastfeeding — it helps with postpartum weight loss, improves glucose metabolism, and reduces the child’s future risk of obesity and diabetes. Maintaining a healthy weight, exercising regularly, and following a balanced diet in the years after pregnancy can delay or prevent the onset of Type 2 diabetes.