Gestational diabetes mellitus (GDM) is high blood sugar that develops during pregnancy in someone who did not have diabetes before. It affects 5% to 9% of U.S. pregnancies, and it usually produces no symptoms at all, which is why nearly every pregnant person gets a glucose test between 24 and 28 weeks. For Black women, the test matters twice over: the immediate pregnancy risks are real, and the long game is steeper. Black women with a history of GDM carry the highest risk of going on to develop type 2 diabetes, and they are screened for it after delivery at some of the lowest rates of any group.
What gestational diabetes is and why it happens
Pregnancy makes the body resist insulin on purpose. The placenta releases hormones, chiefly human placental lactogen, that blunt how well insulin moves sugar out of the blood, which helps route glucose to the growing baby. Most people compensate by making more insulin. GDM happens when the pancreas cannot keep up, so blood sugar climbs. It typically appears around the 24th week, when those placental hormones peak.
This is not the same as type 1 or type 2 diabetes that existed before pregnancy. It is a pregnancy-specific condition, and for most women blood sugar returns to normal soon after the baby is born. The catch is what it predicts about the years that follow, which is the part this article keeps returning to.
It has no symptoms, so screening is everything
GDM rarely announces itself. When symptoms do appear they are mild and easy to write off in pregnancy: more thirst than usual, urinating more often. That is exactly why screening is universal. The standard is a glucose test between 24 and 28 weeks. In the common two-step approach, you drink a 50-gram glucose solution and have blood drawn an hour later; if that screen is high, you return for a 100-gram, three-hour oral glucose tolerance test that confirms the diagnosis. Some clinicians use a one-step 75-gram test instead.
If you have risk factors such as obesity, prior GDM, a previous large baby, or a family history of diabetes, your clinician should screen you earlier, often at the first prenatal visit. A normal early test does not end the matter. Because many people pass early screening and still develop GDM later, the 24-to-28-week test is repeated even after a negative early result.
The risks to baby and mother if it goes uncontrolled
High maternal blood sugar crosses the placenta, and the baby's pancreas responds by making extra insulin, a growth signal. That drives the most common complication, macrosomia, a baby that grows large. A large baby raises the odds of shoulder dystocia and birth injury and makes a cesarean delivery more likely. After birth the baby's own insulin is still running high without the maternal sugar supply, so neonatal hypoglycemia (low blood sugar in the newborn) is a real risk, along with jaundice and breathing trouble.
For the mother, uncontrolled GDM raises the risk of preeclampsia, the dangerous blood-pressure disorder of pregnancy, and of preterm birth before 37 weeks. These risks compound the danger for Black mothers, who already die of pregnancy-related causes at far higher rates and whose preeclampsia is more often caught late. If you want the warning signs spelled out, read our guide to preeclampsia in Black women.
The reassuring half of the picture is that control changes the math. Treating GDM lowers the rate of these complications. In one analysis, preeclampsia risk fell from 18% to 12% with treatment. When blood sugar is well managed, GDM usually leads to a healthy delivery and a healthy baby.
Why this sits at the center of the Black maternal-health gap
GDM is not where the Black maternal disparity ends, but it is where several threads meet. Black mothers in the United States die of pregnancy-related causes at roughly three times the rate of white mothers, and the conditions GDM feeds into, including preeclampsia and the complications of a difficult delivery, are part of that gap. After pregnancy, the disparity sharpens. Among women with a prior GDM diagnosis, one study found Black women had a 74.4% prevalence of chronic health conditions, compared with 58.5% of white women, making them about 2.4 times as likely to carry a chronic condition.
The trouble is not only biology. Research on women screened after GDM found Black women had higher HbA1c levels and were more likely to land in the prediabetes or diabetes range, yet diagnoses were delayed. The authors point to differences in guideline-based care and poor follow-up of abnormal results, not patient effort, as the driver. Care that screens but does not act on the numbers is a recurring failure mode for Black patients.
Management that works
Most GDM is managed without medication. The first-line plan is built from three pieces: checking blood sugar at home (fasting and after meals), an eating plan that controls carbohydrate load, and regular movement, typically about 30 minutes of moderate activity most days, or 150 minutes a week. For many women that is enough to keep numbers in range.
When blood sugar stays high despite those steps, medication is added. Insulin is the standard treatment in pregnancy because it does not cross the placenta. Metformin is an alternative some clinicians use, though it does cross the placenta. Needing medication is not a failure or a sign the pregnancy is doomed; it is a normal part of treating GDM, and the goal is the same either way: blood sugar in range and a healthy delivery.
The postpartum step that gets dropped
This is the part that prevents the next diagnosis, and it is the part most often skipped. GDM usually resolves after delivery, but it leaves a lifetime risk of type 2 diabetes estimated at 50% to 60%. About half of women with GDM go on to develop type 2 diabetes, and Black women carry the highest risk of that progression.
The American Diabetes Association and ACOG recommend a glucose test at 4 to 12 weeks postpartum, specifically a fasting 75-gram oral glucose tolerance test (the OGTT is preferred over an A1C this soon, because pregnancy and delivery distort A1C). After that, testing should continue every 1 to 3 years for life. Yet a meta-analysis found Black women complete postpartum screening at about 33%, the lowest of any group studied, despite carrying the highest progression risk. A test that prevents the disease most likely to follow GDM is the one Black women are least likely to receive.
Put the test on the calendar before you leave the hospital, and ask for it by name at your six-week visit. The same vigilance applies to the days right after birth: know the postpartum warning signs every Black mother should watch for. A history of GDM also raises the odds of GDM in a future pregnancy, so tell any future prenatal provider, and they will screen you early.
How to get care
The right clinician screens you on time, treats high numbers instead of just recording them, and books your postpartum glucose test before you go home. If you want a provider who takes the Black maternal-health gap seriously, you can find a Black OB-GYN or maternal-fetal and endocrine clinician in our directory. Bring three questions to your next visit: when will I be screened for GDM, what are my home blood-sugar targets, and when is my postpartum diabetes test scheduled.
Frequently asked questions
Does gestational diabetes have symptoms? ▼
Usually not. GDM most often causes no symptoms, which is why screening between 24 and 28 weeks is routine. Any symptoms tend to be mild, such as more thirst or urinating more often, and are easy to miss in pregnancy.
When is the gestational diabetes test done? ▼
Between 24 and 28 weeks of pregnancy for most people. If you have risk factors such as obesity, a prior GDM pregnancy, a previous large baby, or a family history of diabetes, your clinician should screen you earlier, often at the first prenatal visit, and again at 24 to 28 weeks.
Will gestational diabetes hurt my baby? ▼
When blood sugar is well controlled, GDM usually leads to a healthy baby. Uncontrolled GDM raises the risk of a large baby, birth injury, preterm birth, newborn low blood sugar, jaundice, and a higher chance of cesarean delivery. Monitoring, an eating plan, movement, and medication when needed bring those risks down.
Does gestational diabetes go away after delivery? ▼
For most women, blood sugar returns to normal soon after birth. But about half of women with GDM develop type 2 diabetes later, and Black women carry the highest risk. That is why the 4-to-12-week postpartum glucose test and ongoing screening every 1 to 3 years matter.
Why are Black women more likely to develop type 2 diabetes after GDM? ▼
The risk reflects both biology and care gaps. Black women with a GDM history have higher rates of chronic conditions and higher post-pregnancy blood-sugar levels, and they are screened after delivery at the lowest rates of any group, around 33%. Delayed follow-up of abnormal results, not patient effort, is a major driver. Getting the postpartum test and keeping up regular screening closes much of the gap.
Is insulin safe to take during pregnancy for GDM? ▼
Yes. Insulin is the standard medication for GDM precisely because it does not cross the placenta to the baby. It is added when an eating plan, movement, and blood-sugar monitoring are not enough. Metformin is an alternative some clinicians use, though it does cross the placenta.
