Blood Sugar Screening (Prenatal)

In order to determine whether you’ve developed gestational diabetes during pregnancy, doctors may test your blood sugar level. The most common procedure is a glucose screening.

Most women are tested between the 24th and 28th weeks of pregnancy, the time when the body is likely to begin having greater difficulty processing glucose. If you are at high risk, your doctor will likely test you much earlier. Pregnancy hormones disrupt your body’s ability to make or use insulin (a hormone produced by the pancreas), which helps turn sugar from food into energy. When these hormones are disrupted, dangerously high amounts of sugar (glucose) can show up in the blood.

Who should have the test?

Guidelines issued by the American Diabetes Association (ADA) recommend that all pregnant women have a risk assessment for gestational diabetes at their first prenatal visit. Women who are known to be at high risk of getting the condition should be screened as soon as possible after their pregnancy is confirmed. According to the ADA, a woman is considered to be high risk with any of the following risk factors:

  • Is severely obese
  • Has a strong family history of type 2 diabetes
  • Has glucose in her urine
  • Has Polycystic Ovary Syndrome, or PCOS (a condition that affects a woman’s menstrual cycle, hormone levels, heart, and blood vessels)
  • Had gestational diabetes in a previous pregnancy
  • Delivered a very large baby in a previous pregnancy

Like many screening procedures, initial glucose screenings have a high false-positive rate. You may simply be one of the 17.9 percent of women who test positive for the condition who aren’t diagnosed with the disorder on follow-up testing. However, if your test results show a fasting blood glucose reading of 90 mg/dl and 140 mg/dl or more an hour after eating, you’ll automatically receive a probable diagnosis of gestational diabetes. In general, your blood glucose will need to be retested on a different day to confirm the diagnosis. Up to 9.2 percent of all pregnant women in the United States develop gestational diabetes, according to federal estimates.

In fact, the 2016 guidelines for gestational diabetes published in Diabetes Care acknowledge that damage to the mother and fetus occurred at lower blood sugar levels than previously thought. Under the new guidelines, a fasting blood sugar level of 91 — previously in the normal range — would qualify for the condition, as would levels (also previously considered normal) of 180 or higher an hour after eating.

What do I do if I’m diagnosed with gestational diabetes?

Simply making some changes to your diet and adding exercise to your day can help keep your blood sugar levels from spiking after you eat. Your doctor or midwife may also refer you to a registered dietitian for nutritional counseling. Together you can work out a diet that provides enough calories and nutrients to keep you from going hungry while controlling your blood sugar level.

Depending on your diet, your counselor may suggest you increase the amount of fiber-rich foods you eat, as well as fruits, vegetables, and whole-grain cereals. You may also be advised to eat smaller meals more often, and to count the number of carbohydrates you eat during the day.

If diet and exercise don’t do the trick, your doctor may also prescribe insulin and recommend monitoring your blood sugar levels daily.

Either way, your health practitioner will closely monitor you and your developing baby to make sure you both stay healthy. Your practitioner may also suggest fetal monitoring to assess the size and well-being of your baby. These tests may include ultrasound exams and nonstress tests (noninvasive, painless procedures) that monitor your baby’s heart rate.

After your baby is born, gestational diabetes usually goes away. But a small number of women continue having higher than normal blood sugar. Your practitioner will want to retest you, usually six to 12 weeks after your baby is born, to make sure you’re free of the disorder.


American Diabetes Association 2016 Guidelines on Gestational Diabetes. National Diabetes Education Institute.

New Guidelines for Gestational Diabetes, LA Times blogs, February 26, 2010. National institutes of Heath, National Institute of Child Health and Human Development

What is gestational diabetes? American Diabetes Association.

National Diabetes Information Clearinghouse. What I need to know about Gestational Diabetes.

U.S. Food and Drug Administration. Women and Diabetes.

March of Dimes. Diabetes in Pregnancy.

National Women’s Health Information Center. Polycystic Ovary Syndrome (PCOS). Frequently Asked Questions.

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