You are 28 weeks pregnant. Your health care provider has just told you that you have gestational diabetes mellitus. Should you be concerned?

The short answer: yes. Good care means a lot for your health and your baby’s health.

What Is Gestational Diabetes?

Pregnant women who have never had diabetes before but who have high blood sugar levels during pregnancy are said to have gestational diabetes. Gestational diabetes affects about 4 percent of all pregnant women—about 135,000 cases in the United States each year.

We don’t know what causes gestational diabetes, but we have some clues. Your placenta supports your baby as he or she grows. Hormones from the placenta help your baby develop. But these hormones also block the normal action of your insulin in your body during pregnancy. This problem is called insulin resistance. Insulin resistance makes it hard for the mother’s body to use insulin. You may need up to three times as much insulin as when you were not pregnant.

Gestational diabetes starts when your body is not able to make and use all the insulin it needs for pregnancy. Without enough insulin. Sugar builds up in the blood to high levels. This is called hyperglycemia.

The American Diabetes Association says that pregnant women who

• are 25 years or older
• were overweight before they became pregnant
• have a family history
• are Hispanic, African, Native, Asian American, or a Pacific Islander

should be screened for gestational diabetes between the 24th and 28th weeks—around the 6th month—of pregnancy. By then, your placenta has begun to make the hormones that lead to insulin resistance.

The screening test measures your blood sugar response to glucose consumed in a drink.

How Gestational Diabetes Can Affect Your Baby

Gestational diabetes affects the mother in late pregnancy, after the baby’s body has been formed, but while the baby is busy growing. Because of this, gestational diabetes does not cause the kinds of birth defects sometimes seen in babies whose mothers had diabetes before pregnancy.

However, untreated or poorly controlled gestational diabetes can hurt your baby. When you have gestational diabetes, your pancreas works overtime to produce insulin, but the insulin does not lower your blood sugar levels. Although insulin does not cross the placenta to your baby, sugar and other nutrients do. So extra blood sugar goes through the placenta, giving the baby high blood sugar levels. This causes your baby’s pancreas to make extra insulin to get rid of the blood sugar.

This can lead to macrosomia, or a "fat" baby. Macrosomia develops because extra blood sugar and insulin cause your baby to make extra fat. Babies with macrosomia face health problems of their own, including damage to their shoulders during birth. Because of the extra insulin made by the baby’s pancreas, newborns may have very low blood sugar levels at birth and may also have a higher risk for breathing problems. Babies with excess insulin become children who are at risk for obesity and adults who are at risk for type 2 diabetes.

Treating Gestational Diabetes

Because this condition can hurt you and your baby, you need to start treatment quickly. Treatment is geared toward keeping blood sugar levels equal to those of pregnant women who don’t have gestational diabetes. Treatment includes special meal plans and scheduled physical activity. It may also include daily blood sugar testing and insulin injections. You will need help from your doctor, nurse educator, dietitian, and other members of your health care team so that your treatment can be changed as needed.

For you as the mother-to-be, treatment for gestational diabetes helps lower the risk of a cesarean section birth that very large babies may require. Sticking with your treatment will give you a healthy pregnancy and birth and help your baby avoid future health problems.

Looking Ahead

Gestational diabetes usually goes away after pregnancy. But once you’ve had gestational diabetes, your chances are 2 in 3 that it will return in future pregnancies. In a few women, however, pregnancy uncovers type 1 or type 2 diabetes. It is hard to tell whether these women have gestational diabetes or have just started showing their diabetes during pregnancy. These women will need to continue diabetes treatment after pregnancy.

Your blood sugar level should be checked six weeks after your baby is born. If your blood sugar level is normal, it should be rechecked at least every three years.

Many women who have gestational diabetes go on to develop type 2 diabetes years later. There seems to be a link between the tendency to have gestational diabetes and type 2 diabetes. Both conditions involve insulin resistance. Certain basic lifestyle changes may help prevent diabetes after gestational diabetes.

Losing weight. If you lose weight, this can help you avoid developing type 2 diabetes.

Making healthy food choices. Follow simple daily guidelines, like eating a variety of foods including fresh fruits and vegetables, limiting the fat

you eat, and watching your portion size. Healthy eating habits can go a long way in preventing diabetes and other health problems.

Exercising. Regular exercise allows your body to use blood sugar without extra insulin. This helps combat insulin resistance and is what makes exercise helpful to people with diabetes. Never start an exercise program without checking with your doctor first.

Keeping Worry in Perspective

While gestational diabetes is a cause for concern, the good news is that you and your health care team—your doctor, obstetrician, nurse educator, and dietitian—work together to lower your high blood sugar levels. And, with this help, you can turn your concern into a healthy pregnancy for you and a healthy start for your baby.