Gestational Diabetes Mellitus
On this page
Direct answer
Gestational diabetes mellitus (GDM) is glucose intolerance first recognised during pregnancy, screened universally in India at 24-28 weeks. The DIPSI (Diabetes in Pregnancy Study Group India) approach uses a single-step, non-fasting 75 g oral glucose load, with a two-hour plasma glucose of 140 mg/dL or more diagnosing GDM. Management begins with medical nutrition therapy and exercise, adding insulin or metformin when glucose targets are not met.
What you must remember
- DIPSI method — 75 g glucose given irrespective of fasting status; a two-hour value of 140 mg/dL or more diagnoses GDM; the single-step strategy is the standard adopted across India.
- IADPSG criteria used elsewhere need a fasting 75 g OGTT — fasting 92, one-hour 180, or two-hour 153 mg/dL or more.
- Screen all pregnant women at 24-28 weeks; test earlier for high-risk women (obesity, prior GDM, family history, previous macrosomia, PCOS).
- Medical nutrition therapy with a dietitian plus moderate exercise is first line; drugs are added when targets are unmet despite lifestyle effort.
- Insulin is the traditional gold standard as it does not cross the placenta; metformin is an accepted alternative with reassuring safety data, though it does cross the placenta.
- Common targets — fasting around 95 mg/dL or less, one-hour postprandial 140 or less, and two-hour postprandial 120 mg/dL or less.
- Risks — macrosomia with shoulder dystocia, neonatal hypoglycaemia, hyperbilirubinaemia, respiratory distress and prematurity; maternal pre-eclampsia and a high lifetime risk of type 2 diabetes. Perform a 75 g OGTT at six to twelve weeks postpartum to exclude persistent diabetes.
Common confusion
GDM is confused with overt (pre-existing) diabetes first detected in pregnancy. Very high values early in pregnancy — fasting 126 mg/dL or more, random 200 or more with symptoms, HbA1c 6.5 per cent or more — indicate overt diabetes, managed as pre-existing disease. Students also mix up the DIPSI and IADPSG numbers; DIPSI needs only the single non-fasting two-hour value of 140 mg/dL — the figure asked in Indian exams.
Exam-focused takeaway
Expect DIPSI threshold one-liners, the 24-28 week screening window, and drug-choice stems — insulin as the classical gold standard with metformin acceptable. Know the macrosomia-shoulder dystocia chain, neonatal hypoglycaemia as the immediate postnatal worry, and the six-to-twelve-week postpartum OGTT for follow-up.
Frequently asked questions
What are the DIPSI criteria for GDM?
A 75 g oral glucose load taken irrespective of fasting, with a two-hour plasma glucose of 140 mg/dL or more diagnosing GDM. It combines screening and diagnosis in a single step.
When is screening for GDM performed?
Universally at 24-28 weeks of gestation. Women with high-risk factors are tested earlier in pregnancy and retested in the third trimester if initially normal.
What is the first-line management of GDM?
Medical nutrition therapy and moderate physical activity, with glucose self-monitoring. Pharmacotherapy is added if targets are not achieved.
Which drugs treat GDM when lifestyle measures fail?
Insulin remains the gold standard because it does not cross the placenta; metformin is a widely accepted oral alternative. Oral sulfonylureas are largely avoided.
What neonatal complications follow poorly controlled GDM?
Macrosomia with shoulder dystocia and birth injury, neonatal hypoglycaemia, hyperbilirubinaemia, respiratory distress syndrome and prematurity — hence close neonatal glucose monitoring.
What follow-up is needed after delivery?
A 75 g OGTT at six to twelve weeks postpartum to exclude persistent diabetes, then lifelong periodic screening because of the high risk of type 2 diabetes.