Gestational diabetes develops when your body can’t produce enough insulin to keep up with the demands of pregnancy. What determines whether you get it comes down to a combination of how your body handles insulin before pregnancy, hormonal changes during pregnancy, and several measurable risk factors including weight, age, family history, and ethnicity. About 2% to 10% of pregnancies in the United States are affected each year.
How Pregnancy Changes Blood Sugar Processing
During pregnancy, the placenta produces hormones that help your baby grow. These same hormones make your cells less responsive to insulin, the hormone that moves sugar out of your bloodstream and into your cells for energy. This is called insulin resistance, and it happens in every pregnancy to some degree. Your pancreas compensates by producing more insulin, sometimes two to three times the normal amount.
Gestational diabetes develops when your pancreas can’t keep up with the extra demand. The sugar stays in your blood instead of being absorbed by your cells, and blood sugar levels rise above normal. This typically becomes most pronounced in the second half of pregnancy, which is why routine screening happens between 24 and 28 weeks.
Pre-Pregnancy Weight
Being overweight before pregnancy is one of the strongest predictors. Extra body fat, particularly around the abdomen, increases insulin resistance even before pregnancy begins. When pregnancy hormones add their own insulin-blocking effect on top of that existing resistance, the pancreas faces a much steeper challenge. Women who enter pregnancy at a higher weight are significantly more likely to develop gestational diabetes than those at a moderate weight.
Family History and Genetics
A family history of type 2 diabetes raises your risk substantially. If a parent or sibling has type 2 diabetes, you likely share genetic traits that affect how efficiently your body produces or uses insulin. These same traits make it harder for your pancreas to ramp up insulin production during pregnancy.
Ethnicity plays a notable role, and the differences in prevalence are striking. CDC data from 2020 shows that non-Hispanic Asian women had the highest rate of gestational diabetes at 14.9%, followed by non-Hispanic American Indian and Alaska Native women at 11.8%, and non-Hispanic Native Hawaiian and Pacific Islander women at 10.6%. Hispanic women had a rate of 8.5%, while non-Hispanic White women were at 7.0% and non-Hispanic Black women at 6.5%.
Within these broader groups, the variation is even more granular. Among Asian subgroups, Asian Indian women had the highest rate at 16.7%, while Japanese women had the lowest at 9.3%. Among Hispanic subgroups, Mexican women had the highest rate at 8.9% and Central and South American women the lowest at 7.5%. These patterns suggest that specific genetic backgrounds influence insulin function during pregnancy in ways researchers are still working to fully map.
PCOS and Insulin Resistance
Polycystic ovary syndrome is a particularly important predisposing condition. Women with PCOS often have insulin resistance as a baseline feature of the condition, meaning their bodies produce insulin but can’t use it effectively. When pregnancy adds further insulin resistance on top of that, the combined effect can overwhelm the pancreas. If you have PCOS, your risk of gestational diabetes is elevated regardless of your weight, though carrying extra weight compounds it.
Previous Pregnancy History
Having gestational diabetes in a previous pregnancy is one of the clearest predictors that it will happen again. The recurrence rate is high because the underlying factors, your pancreas’s capacity and your baseline insulin sensitivity, tend to remain the same or worsen between pregnancies, especially if weight increases.
Delivering a baby weighing over 9 pounds in a prior pregnancy is also a risk factor. A large baby can be a sign that blood sugar was running higher than normal during that pregnancy, even if gestational diabetes was never formally diagnosed. Your provider may use this history as a reason to screen you earlier.
Maternal Age
The older you are during pregnancy, the higher your risk. Insulin sensitivity naturally decreases with age, and the pancreas becomes less efficient at compensating. Women over 25 face a higher risk than younger women, with the risk continuing to climb through the 30s and 40s. This is one reason gestational diabetes rates have been increasing overall, as the average age of first pregnancy has risen.
How and When Screening Happens
Most pregnant women are screened for gestational diabetes between 24 and 28 weeks, the window when placental hormones are driving insulin resistance highest. The standard approach involves drinking a sugary solution and having your blood drawn to measure how well your body processes the sugar.
If you have known risk factors, such as a previous gestational diabetes diagnosis, PCOS, obesity, or high glucose levels detected at a routine prenatal visit, your provider will likely test you earlier in the first trimester. Early detection matters because unmanaged high blood sugar in the first weeks of pregnancy carries risks for both fetal development and pregnancy complications.
What Happens After Delivery
For most women, blood sugar returns to normal after the placenta is delivered and those insulin-blocking hormones drop. But gestational diabetes is a strong signal about your long-term metabolic health. Women who develop it have a significantly elevated risk of developing type 2 diabetes later in life. Having had gestational diabetes essentially reveals a vulnerability in your insulin system that pregnancy stress exposed but that aging, weight gain, or inactivity could trigger again outside of pregnancy.
Postpartum blood sugar testing is typically recommended 6 to 12 weeks after delivery and then periodically going forward. Maintaining a moderate weight, staying physically active, and eating in ways that avoid sharp blood sugar spikes are the most effective ways to reduce the chance of progressing to type 2 diabetes after a gestational diabetes diagnosis.