Gestational Diabetes Mellitus

While almost all pregnant women experience higher glucose levels during pregnancy, not all develop gestational diabetes mellitus (GDM). In fact, gestational diabetes mellitus can occur in up to 18% of pregnancies, according to estimates released by the American Diabetes Association. The disorder occurs even in cases where the mother has no history and no risk factors for diabetes.

Commonly diagnosed at about 24 weeks of pregnancy, GDM is believed to be the result of hormones from the placenta blocking the efficient action of insulin in the mother’s body. This is called insulin resistance, and it can result in the mother’s body needing as much as three times the normal amount of insulin to process sugar intake.

When the mother’s body cannot create enough insulin to meet these needs, glucose levels begin to rise in the mother’s bloodstream. This is gestational diabetes mellitus.

Insulin does not cross the placenta, but glucose does. When the extra glucose in the mother’s body crosses into the baby, this causes over-nutrition and the baby’s pancreas goes into overdrive, creating more insulin to try to process the sugar load. Because this is more energy than the baby needs, the excess is stored as fat in the baby’s body.

Risks for Big Babies

The excess fat the baby stores is called “macrosomia.” This fat storage increases the baby’s birth weight, which can lead to a host of health issues. Often, these large babies must be delivered by caesarean section. Even if the baby is delivered vaginally, they are at increased risk for complications, including the need for a forceps delivery, damage to their shoulders during birth and other birth trauma.

Once the baby is born and the excess glucose is no longer entering the baby’s bloodstream, the baby’s pancreas might not slow its production of insulin fast enough. The excess insulin still being produced postpartum could cause the baby’s blood sugar to drop too low, leading to hypoglycemia.

Other postpartum risks to the child include an increased incidence of jaundice, and breathing problems.

Who is At Risk

There are certain factors that increase the risk of developing GDM:
 Women who are more than 20% above their ideal body weight prior to pregnancy;
 Being a member of an at-risk ethnic group (Hispanic, Black, Asian or Native American);
 Pre-diabetic prior to pregnancy;
 Previously giving birth to a baby more than 9 pounds;
 Previously delivering a stillborn baby;
 Having gestational diabetes during a previous pregnancy;

How Gestational Diabetes is Diagnosed

Generally, women who are determined to be at high risk for GDM are screened early in the pregnancy. For all other women, and for at high risk mothers whose initial screenings were normal, screening is recommended between 24 and 28 weeks of pregnancy.

The test used for screening is the Oral Glucose Tolerance Test (OGTT), which involves drinking a solution containing a measured amount of sugar, and then having blood drawn one hour later. This test measures how efficiently the mother’s body has metabolized the sugar. If this test is positive for high glucose levels (above 140 mg/dl) then a second fasting glucose test will be given at a later date.

How Gestational Diabetes is Managed

Doctors will advise women with GDM to monitor and manage their disease using methods similar to those used by type 2 diabetes patients. These include monitoring blood sugar, moderate exercise, diet control and possibly taking insulin.

Once a mother with gestational diabetes gives birth, it can take as much as six weeks for her sugar levels to return to normal. Some doctors will recommend an additional oral glucose tolerance test up to three months after delivery, to make certain that there is no further issue with insulin resistance.

Future Risks of Developing Diabetes

A mother who develops GDM during one pregnancy has a 40% to 50% risk of developing diabetes with a subsequent pregnancy. In addition, she has a 35% to 60% additional risk of developing type 2 diabetes over the next 10 to 20 years, according to National Institutes of Health statistics.

An infant born to a mother with gestational diabetes has an increased risk of developing diabetes in the future, as well as an increased risk of becoming overweight during childhood.

Photo by John Nyboer