Gestational diabetes is a type of diabetes that develops during pregnancy in someone who didn’t have diabetes before. It affects how your cells use sugar, causing blood sugar levels to rise higher than normal. The condition typically appears in the second half of pregnancy and resolves after delivery, but it requires careful management to protect both your health and your baby’s.
Why Pregnancy Causes Insulin Resistance
During the first half of pregnancy, your body actually becomes more sensitive to insulin, the hormone that moves sugar from your blood into your cells for energy. But as the placenta grows, it releases a mix of hormones that progressively block insulin’s effects. By the second and third trimesters, insulin sensitivity can drop by up to 60%.
The placenta produces several hormones responsible for this shift. Placental growth hormone reduces your body’s production of a protein that helps insulin work and physically blocks sugar from entering muscle and fat cells. Leptin, which rises early in pregnancy, triggers inflammatory signals in the placenta that further dampen insulin’s ability to do its job. Another hormone called resistin acts on the pancreas itself, reducing the amount of insulin released, while also making muscle, fat, and liver tissue less responsive to whatever insulin is available.
In most pregnancies, the pancreas compensates by producing more insulin. A hormone called human placental lactogen actually stimulates the pancreas to grow more insulin-producing cells to keep up with demand. Gestational diabetes develops when this compensation falls short. Either the pancreas can’t ramp up insulin production enough, or the resistance is too steep to overcome. The result is blood sugar that stays elevated after meals and sometimes between them.
Who Gets Screened and When
The U.S. Preventive Services Task Force recommends screening all pregnant people at 24 weeks of gestation or after, with most testing completed before 28 weeks. If you enter prenatal care later than that, screening still happens but on a shifted timeline.
Some people are screened earlier in pregnancy because they carry risk factors for type 2 diabetes. These include obesity, a family history of type 2 diabetes, or having delivered a large baby in a previous pregnancy. If any of these apply, your provider may test you in the first trimester rather than waiting until the standard window.
How the Diagnosis Works
The most common approach in the U.S. is a two-step process. First, you drink a sugary solution and have your blood drawn one hour later. If that initial result is elevated, you return for a longer, more definitive test: the three-hour oral glucose tolerance test. You fast overnight, have your blood drawn, drink a higher-concentration glucose solution, and then have your blood tested at the one-hour, two-hour, and three-hour marks.
The thresholds for that three-hour test are:
- Fasting: 95 mg/dL or higher
- One hour: 180 mg/dL or higher
- Two hours: 155 mg/dL or higher
- Three hours: 140 mg/dL or higher
Two or more abnormal values on this test confirm a gestational diabetes diagnosis. A single abnormal value doesn’t meet the threshold, though your provider may still recommend closer monitoring.
Risks for You and Your Baby
Unmanaged gestational diabetes raises the odds of several complications. For your baby, the primary concern is macrosomia, meaning the baby grows larger than expected because excess sugar in your blood crosses the placenta and stimulates extra growth. A large baby increases the likelihood of a difficult delivery, birth injuries, and cesarean section. After birth, babies exposed to high blood sugar in the womb can experience drops in their own blood sugar once they’re no longer receiving that excess supply.
For you, gestational diabetes significantly increases the risk of preeclampsia, a dangerous condition involving high blood pressure and organ stress. The combination of gestational diabetes and preeclampsia raises the chance of preterm delivery and further increases the likelihood of cesarean birth. Excessive weight gain during the middle and later trimesters compounds these risks. Gaining too much weight in the second trimester is linked to larger babies, while excessive gain in the third trimester is a risk factor for severe preeclampsia.
The effects can extend beyond pregnancy as well. Having both gestational diabetes and preeclampsia raises a mother’s long-term risk of chronic high blood pressure, cardiovascular disease, and type 2 diabetes. Children born from these pregnancies tend to show steadily increasing body mass over time.
Managing Blood Sugar During Pregnancy
Treatment starts with two things you control directly: what you eat and how you move. The goal of dietary changes is to spread carbohydrate intake across the day so blood sugar doesn’t spike after any single meal. This typically means smaller, more frequent meals with a consistent balance of carbohydrates, protein, and fat at each one. Many people work with a dietitian to build a meal plan that fits their preferences while keeping blood sugar stable.
Exercise is the other cornerstone. Guidelines recommend both aerobic activity (like walking, swimming, or cycling) and resistance training at moderate intensity, at least three times a week for 30 to 60 minutes per session. For aerobic exercise, continuous sessions of up to 30 minutes work well, or up to 45 minutes if you set your own pace. The key is consistency: no more than two consecutive days without some form of activity. For resistance work, aim for two to three sessions per week with 5 to 10 exercises, doing 8 to 15 repetitions at a moderate effort level.
You’ll also check your blood sugar regularly at home, typically before breakfast and one to two hours after meals, using a small finger-prick glucose meter. These numbers help you and your provider see whether diet and exercise are keeping things in range.
When Lifestyle Changes Aren’t Enough
For some people, dietary changes and exercise don’t bring blood sugar down to target levels. When that happens, medication becomes necessary. Insulin is the primary option because it doesn’t cross the placenta, making it the safest choice for the baby. You’d inject it using a small needle, usually before meals or at bedtime depending on which blood sugar readings are running high.
Some providers prescribe oral medications as an alternative, though insulin remains the standard recommendation when lifestyle measures fall short. The decision depends on how far above target your numbers are and how your body responds to initial treatment adjustments.
What Happens After Delivery
For most people, blood sugar returns to normal shortly after the placenta is delivered, since the hormones driving insulin resistance disappear. But gestational diabetes is a strong signal about your long-term metabolic health. The risk of developing type 2 diabetes is about 7% within five years of a gestational diabetes diagnosis and climbs to 21% within ten years.
Because of this, follow-up testing is recommended starting as early as 4 to 6 weeks after delivery and ideally within the first year postpartum. If that initial test comes back normal, you should still be screened at least every three years for a minimum of ten years. If the early postpartum test is abnormal, a repeat test at six months postpartum helps confirm whether you’ve transitioned to type 2 diabetes or whether the abnormal result was lingering from pregnancy.
The same habits that help manage gestational diabetes, regular physical activity and a balanced approach to carbohydrates, are also the most effective tools for reducing your long-term type 2 risk. Many people find that the dietary patterns and exercise routines they built during pregnancy become a foundation for lasting changes.