Gestational Diabetes: The Screening, and What a Diagnosis Actually Means

Why it happens

The placenta produces hormones that make the body more insulin-resistant as pregnancy progresses — a normal adaptation that helps ensure the baby gets enough glucose. In most people, the pancreas produces enough extra insulin to compensate. Gestational diabetes happens when it can't keep up with the added demand.

The screening test

Most people are screened between 24-28 weeks with a glucose challenge test: you drink a sugary solution, and blood sugar is checked an hour later. If that result is elevated, a longer follow-up test (the 3-hour glucose tolerance test, done fasting) confirms or rules out the diagnosis. Screening earlier in pregnancy is done for people with risk factors — a prior GDM diagnosis, obesity, PCOS, or a strong family history of diabetes.

What changes with a diagnosis

Most gestational diabetes is managed with diet changes (carbohydrate counting and timing, in particular) and regular blood sugar checks at home, several times a day. About 10-20% of people also need medication — insulin or, in some cases, oral medication — when diet and monitoring alone aren't keeping blood sugar in range. This isn't a failure of effort; some cases simply need more support than lifestyle changes provide.

Additional third-trimester monitoring (growth ultrasounds, fetal well-being checks) becomes part of routine care, since GDM raises the chance of a larger-than-average baby and a few other complications that are easier to manage when tracked.

After delivery

Blood sugar typically returns to normal after birth, but gestational diabetes meaningfully raises the lifetime risk of developing type 2 diabetes later — roughly 50% over the following years without intervention. A glucose test at the postpartum visit (usually 4-12 weeks after delivery) checks whether blood sugar has normalized, and ongoing screening every 1-3 years afterward is the standard recommendation.