Gestational Diabetes: What You Need to Know

This pregnancy complication is more common than you might think. Learn what causes gestational diabetes, who's at risk for it, how it's detected, and what can be done to treat it.

Here are a few things that might surprise you about gestational diabetes (GDM), or diabetes that develops in about 9 percent of women during pregnancy.

For years, doctors believed that gestational diabetes affected three to five percent of all pregnancies, but new, more rigorous diagnostic criteria puts the number closer to 18 percent—it's more common than previously understood. The condition, which can strike any pregnant woman, usually develops in the second trimester, between weeks 24 and 28, and typically resolves after baby is born.

If gestational diabetes is treated and well-managed throughout your pregnancy, "There's no reason you can't deliver a very healthy baby," says Patricia Devine, M.D., perinatologist at New York-Presbyterian Hospital in New York City. But gestational diabetes that goes untreated, or isn't carefully monitored, can be harmful for both mother and baby. Consult our guide for risk factors, signs of gestational diabetes, and treatment options.

What is gestational diabetes?

Gestational diabetes, or diabetes that is diagnosed during pregnancy in a woman who previously did not have diabetes, occurs when the pancreas fails to produce enough insulin to regulate blood sugar efficiently. "A hormone produced by the placenta makes a woman essentially resistant to her own insulin," Dr. Devine explains.

How does gestational diabetes differ from type 1 or 2 diabetes?

Gestational diabetes affects only pregnant women. People who have type 1 diabetes, sometimes referred to as juvenile diabetes, are generally born with it. Type 2 diabetes accounts for 95 percent of all cases of diabetes in the U.S.; it occurs in adulthood and is triggered by lifestyle factors such as obesity and lack of physical activity.

What causes gestational diabetes?

It's unclear why some women develop gestational diabetes while others do not. Doctors theorize that genetic predisposition, environmental issues (such as obesity prior to pregnancy), and/or behavioral factors (such as diet and exercise habits) may contribute.

In 2014, the Centers for Disease Control and Prevention (CDC) reported that 1 in 10 American pregnant women develop diabetes during pregnancy, with obesity standing out as the major risk factor for the disease, just as it is with type 2 diabetes. 

According to the CDC's study, women who've never been diabetic before but who have high blood sugar during pregnancy can develop gestational diabetes. The Centers found a link between increasing rates of gestational diabetes and a rise in obesity in the U.S. 

For women who've gained a significant amount of weight during pregnancy and are "borderline" diabetic, Elizabeth Pryor, M.D., FACOG, recommends discussing with your doctor the development of a diet plan so that you can minimize weight gain for the remainder of the pregnancy. "Women who gain significant weight in pregnancy tend to deliver large babies," said Dr. Pryor. "If your diabetes test is borderline, your doctor may consider repeating it later in pregnancy. Certain things that you can avoid that may help include soda drinks, juices, and ice cream. These are common culprits."

Risk factors 

Although the condition can strike any pregnant woman, there are several factors that could increase your chances of developing it. Risk factors include:

  • Age greater than 25
  • Family history of diabetes
  • Obesity prior to pregnancy
  • History of birthing big babies (over 9 pounds)
  • High blood pressure
  • Excess amniotic fluid (called polyhydramnios)
  • History of unexplained miscarriage or stillbirth
  • Personal history of gestational diabetes
  • Being African American, Hispanic, American Indian, Alaska Native, Native Hawaiian, or Pacific Islander

What are the signs of gestational diabetes?

Many women with gestational diabetes have either no symptoms or very mild symptoms. Possible symptoms include fatigue, excessive thirst, blurred vision, frequent urination, weight loss despite an increased appetite, nausea, and vomiting.

Once you've had it, how likely are you to get it again?

If you've had gestational diabetes in a previous pregnancy, you have a 60 percent chance of developing it again, according to the American Diabetes Association. Additionally, half of all women with a history of gestational diabetes develop type 2 diabetes within 10 years of the onset of their gestational diabetes, so it's important to maintain good exercise and nutritional habits after your baby is born.

How is it diagnosed?

Around 20 weeks, pregnant women are given a gestational diabetes test in the form of a standard glucose screening that consists of swallowing a concentrated glucose substance and having blood-sugar levels tested one hour later. If elevated blood-sugar levels are detected, a more thorough glucose tolerance test will be given, which involves an overnight fast, drinking another glucose beverage, and more blood work.

This simple test looks for potential cases of gestational diabetes, to help prevent complications in your pregnancy.

Gestational diabetes treatment

Your doctor will recommend diet modifications, such as limiting carbohydrates, and regular exercise to get the condition under control quickly and normalize blood sugar levels. But some women may require daily glucose testing and more intensive treatment, such as insulin injections.

Also, taking certain supplements—vitamin D and calcium, specifically—may lower blood sugar readings and improve other measures of metabolic health that can suffer with gestational diabetes, according to an Iranian study from 2014. The research, which was published in the journal Diabetologia, compared blood levels of women with gestational diabetes—some of whom had been given vitamin D and calcium supplements, and some of whom were given placebo pills—and found that "fasting blood glucose and cholesterol levels improved" in the supplement group but not the placebo group, according to the New York Times

The findings come with a caveat, however: "Vitamin D has some toxic effects on women and their babies, so we cannot recommend that all women should take it," said the study's senior author, Ahmad Esmaillzadeh, M.D., an associate professor at the Isfahan University of Medical Sciences.  "But we can recommend it for people with gestational diabetes who are vitamin D deficient."

How does gestational diabetes affect the developing baby?

You can help minimize your baby's chances of developing complications by carefully managing your gestational diabetes. The condition can cause a newborn to grow very big in utero (over 9 pounds), which may result in a traumatic delivery in which your baby could be injured. Having a very large baby also dramatically increases your chances of needing a cesarean section. Other potential problems for the baby include hypoglycemia (very low blood sugar), jaundice, electrolyte abnormalities, seizures, and breathing problems due to immature lungs (called respiratory distress syndrome).

Furthermore, a new study published by the Archives of Pediatrics & Adolescent Medicine found that children born to mothers who had gestational diabetes are twice as likely to meet the criteria for attention deficit hyperactivity disorder (ADHD) by age 6 as those whose mothers did not develop the condition. They may also be at risk for developing Type 2 diabetes later in life.

 Holly Lebowitz Rossi also contributed to this article. 

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