Gestational diabetes: high blood sugar in pregnancy

Gestational diabetes affects about six per cent of pregnancies in Canada. Like type 2 diabetes, gestational diabetes is a condition in which the body has trouble making or using a hormone called insulin, which is produced in the pancreas.

Insulin controls blood sugar levels, so insufficient insulin can lead to high blood sugar. When those levels are too high, it poses risks for the baby.

“Because gestational diabetes only comes up in the second half of pregnancy after all the organs have formed, the main risk is that the baby overgrows,” says Dr. Lorraine Lipscombe, director of the Centre for Integrated Diabetes Care at Women’s College Hospital (WCH). “The baby grows too much because they have to secrete more insulin in order to get those sugars down, and insulin is a growth factor.”

Large babies have increased risks for complicated deliveries, such as difficulty with vaginal deliveries, increased C sections, and shoulder trauma during delivery (shoulder dystocia).

Gestational diabetes may also have some longer-lasting effects on the baby.

“There is evidence emerging that if they are exposed to high blood sugars in pregnancy, the baby’s pancreas has to work harder and that can lead to a potential increased risk of diabetes and insulin secretory defects in the baby,” Dr. Lipscombe explains. “So that’s the other concern: that over the years it predisposes the baby to a higher risk of type 2 diabetes, so it’s a vicious cycle.”

One of the goals of identifying and treating gestational diabetes is to avoid these short-term and long-term risks to the baby.

Women with gestational diabetes are usually cared for by specialists during pregnancy. They need to monitor their blood sugar levels several times a day, and make diet changes to try to control their blood sugars. However, even with diet changes, about 40 to 50 per cent of these women will need to take insulin to keep their blood sugar under control.

In about 70 per cent of cases, gestational diabetes goes away after delivery.

“The other 30 per cent of women will either have pre-existing type 2 diabetes that was present even before they got pregnant, but not diagnosed, or they might have pre-diabetes,” Dr. Lipscombe says.

However, all women who have had gestational diabetes are at increased risk for developing type 2 diabetes later in life. The gestational diabetes does not cause this risk, but is actually a result of pre-existing risk factors.

“Women get gestational diabetes because they have risk factors for type 2 diabetes, but it hasn’t developed yet,” Dr. Lipscombe explains. “The pregnancy places increased stress on their body, and leads to this glucose abnormality.”

Because gestational diabetes is an early sign of long-term risk for type 2 diabetes, the risk factors are the same as those for type 2 diabetes:

• being obese or overweight
• gestational diabetes in a previous pregnancy
• family history of type 2 diabetes
• polycystic ovary syndrome (PCOS)
• high-risk ethnicity, such as Aboriginal, African, Asian, South Asian, Caribbean or Hispanic descent

Although risk factors like family history cannot be changed, it may be possible to reduce risks of pregnancy complications, including gestational diabetes, by improving lifestyle habits. The challenge is making those changes before becoming pregnant.

“A lot of women delay childbirth these days, so when they eventually go to their doctor to prepare for pregnancy, it’s very hard for them to first lose weight and improve their diet and physical activity before becoming pregnant” Dr. Lipscombe says. “Women don’t want to wait any longer to get pregnant.”

There are also benefits to adopting – or maintaining – healthy lifestyle choices after pregnancy. Having a healthy BMI, eating a balanced diet and getting regular exercise reduces the long-term risk of type 2 diabetes in high-risk women, including those who have had gestational diabetes.