Pregnancy diabetes, known medically as gestational diabetes, is a type of diabetes that develops during pregnancy in women who didn’t have diabetes before. It affects about 8.3% of pregnancies in the United States, up from 6% just five years earlier. Unlike other forms of diabetes, gestational diabetes usually resolves after delivery, but it requires careful management to protect both mother and baby.
Why Pregnancy Causes Diabetes
Your placenta does more than nourish your baby. It also produces hormones, including estrogen, cortisol, and one called human placental lactogen, that help maintain the pregnancy. A side effect of these hormones is that they interfere with how your body uses insulin, the hormone responsible for moving sugar out of your blood and into your cells. This interference typically kicks in around 20 to 24 weeks of pregnancy and gets stronger as the placenta grows larger.
Normally, your pancreas compensates by producing extra insulin. In gestational diabetes, the pancreas can’t keep up with the increased demand. Sugar builds up in the bloodstream instead of being absorbed by cells. This is not caused by a lack of insulin the way type 1 diabetes is. It’s caused by insulin becoming less effective, a state called insulin resistance.
Who Is More Likely to Develop It
Several factors raise the risk. Being overweight or obese before pregnancy is one of the strongest predictors. The higher your pre-pregnancy BMI, the greater the likelihood. Age also plays a role: CDC data shows that mothers aged 40 and older are diagnosed at a rate of 15.6%, nearly six times the rate of mothers under 20 (2.7%).
Ethnicity matters too. In the United States, Asian women (particularly South Asian), Black, American Indian, and Hispanic women face the highest risk, mirroring the patterns seen in type 2 diabetes. Other risk factors include a family history of diabetes, having had gestational diabetes in a previous pregnancy, and polycystic ovary syndrome.
How It’s Detected
Screening for gestational diabetes typically happens between 24 and 28 weeks of pregnancy, right when placental hormones start creating the most insulin resistance. If you have elevated risk factors, your doctor may test you at your first prenatal visit instead of waiting.
The most common approach is a two-step process. First, you drink a sugary solution and have your blood drawn one hour later. A blood sugar level below 140 mg/dL is generally considered normal. A result of 190 mg/dL or higher means gestational diabetes is diagnosed right away. If your result falls between those numbers, you’ll take a second, longer test where your blood sugar is checked every hour for three hours after drinking an even sweeter solution. If two or more of those readings come back higher than expected, you’re diagnosed with gestational diabetes.
Risks to Your Baby
When your blood sugar runs high, the extra sugar crosses the placenta and reaches your baby. Your baby’s pancreas responds by producing more insulin, and that excess insulin acts like a growth hormone. This is why 15% to 45% of babies born to mothers with gestational diabetes are unusually large, a condition called macrosomia. Women with gestational diabetes are two to three times more likely to deliver a large baby compared to women without it. A larger baby increases the chance of a difficult delivery, birth injuries, and the need for a cesarean section.
After birth, the baby’s pancreas is still producing extra insulin even though the high sugar supply from the mother has stopped. This can cause the baby’s blood sugar to drop dangerously low. In one large study of over 2,000 pregnant women screened at 24 to 28 weeks, neonatal low blood sugar occurred in about a third of babies born to mothers with gestational diabetes. Medical teams monitor for this closely in the first hours after birth.
The effects can also extend into your child’s future. Children exposed to gestational diabetes in the womb face roughly double the risk of developing metabolic syndrome, a cluster of conditions including obesity, abnormal blood sugar, and cardiovascular problems, later in life.
Risks to You
Gestational diabetes also raises your own health risks during pregnancy. The most significant is preeclampsia, a dangerous condition involving high blood pressure and organ stress. Women with gestational diabetes have about 90% higher odds of developing preeclampsia compared to women without it, with rates of 2.6% versus 1.2%.
After delivery, gestational diabetes usually goes away. But having it signals that your body already struggles with insulin resistance, which puts you at meaningfully higher risk for developing type 2 diabetes in the years that follow. Initial follow-up testing should happen within the first year after delivery, ideally as early as four to six weeks postpartum. Even if that test comes back normal, you should be screened at least every three years for a minimum of 10 years afterward.
Managing Blood Sugar During Pregnancy
The first line of treatment is changing what and how you eat. You’ll typically be referred to a dietitian who can help you build a meal plan. The core principles are straightforward: eat three regular meals a day without skipping any, choose foods that release sugar slowly (whole wheat pasta, brown rice, oats, beans, lentils), load up on fruits and vegetables, and cut back on sugary snacks and drinks. You don’t need to eliminate sugar entirely, but swapping biscuits and cake for fruit, nuts, and seeds makes a real difference in keeping blood sugar stable.
Exercise is the other major tool. Regular physical activity directly lowers blood sugar. The general recommendation is at least 150 minutes of moderate activity per week, things like brisk walking or swimming, plus strength exercises on two or more days. Your care team can advise on what’s safe for your stage of pregnancy.
If diet and exercise don’t bring your blood sugar into a safe range within one to two weeks, or if your levels are very high at diagnosis, medication becomes necessary. The usual first option is metformin, a tablet. Insulin injections are recommended if metformin isn’t enough on its own, causes side effects, or if the baby is already measuring very large. Throughout this process, you’ll be asked to check your blood sugar multiple times a day, typically before meals and after eating, to track how well your management plan is working.
What Happens After Delivery
For most women, blood sugar returns to normal once the placenta is delivered and those insulin-blocking hormones leave the system. Your care team will check your levels in the days after birth to confirm this. A formal glucose tolerance test is recommended within the first year postpartum, and many providers schedule it around six weeks after delivery.
If that early postpartum test comes back positive, a repeat test at least six months after delivery is needed to confirm whether you’ve developed persistent diabetes. For women whose results are normal, the recommendation is screening every three years for at least a decade. Maintaining a healthy weight, staying physically active, and following the same dietary principles that helped during pregnancy are the most effective ways to reduce your long-term risk of type 2 diabetes.