Diabetes and Pregnancy
Diabetes is present in 2-6% of pregnant women in the United States; 88% of these women have gestational diabetes (GDM). This is a form of diabetes which appears during pregnancy, typically during the second or third trimester. The prevalence of GDM has increased due to the increased incidence of obesity in the US. The remaining 12% of pregnant women with diabetes have pre-existing type 1 or type 2 diabetes.
In all women who become pregnant, increased production of hormones by the placenta, such as human placental lactogen, causes resistance to insulin's action. Normal women are able to overcome this by increased production of insulin. Their sugar levels are thus maintained in the normal range.
Women with GDM, as well as pre-existing type 1 and type 2 diabetes, are unable to compensate for pregnancy associated insulin resistance. In type 1 diabetes, this is due to absence of insulin production. In GDM and type 2 diabetes this is due to pre-pregancy insulin resistance. Many of these women may also have defects in insulin production. Their inability to compensate for pregnancy related insulin resistance results in elevation of blood sugar levels.
If sugar levels are increased in women with pre-existing diabetes during the first weeks of pregnancy, there is an increased risk of spontaneous abortions and birth defects. If sugar levels remain elevated throughout their pregnancy, there is an increased risk of large babies and delivery associated injuries. There may also be an increased lifetime risk for obesity and/or diabetes in the child. Elevated sugar levels are also associated with an increased risk of high blood pressure and preeclampsia. High sugar levels in women with GDM are associated with similar risks.
Given the known association of high blood sugar levels with complications in the newborn and mother, good sugar control is important. Among women with pre-existing diabetes, every effort should be made to normalize blood sugar levels before conception.
Once pregnant, typical goals for sugar levels are morning fasting sugars of 70-90 mg/dl and 1 hour after meal sugars <120 mg/dl. HA1c levels should be as close to normal as possible. 70-80% of women with GDM will be able to achieve these goals with changes in their diet and light exercise. Consultation with a nutritionist is important.
If sugar goals are not achieved with lifestyle changes, medical therapy is initiated. In women with pre-existing diabetes, insulin is the most common therapy. Among women with GDM, treatment with oral diabetes agents such as Glyburide is another option.
Many endocrinologists (myself included) prefer insulin therapy due to lack of long-term safety data, as well as less dosing flexibility, with the oral agents. Sugar levels will return to pre-pregnancy values after delivery.
If nursing is planned, medication regimens should be reviewed with an obstetrician. Women with GDM are at a significantly increased risk for developing diabetes in the future. A glucose tolerance test is typically performed 6 weeks after delivery in GDM. Even if the test is normal, efforts should be made to maintain a healthy lifestyle and weight.
If sugar levels are managed carefully in pregnant women with diabetes, the chances for a healthy pregnancy and healthy child are similar to those reported in non-diabetic women. Future advances in management, as well as earlier diagnosis, should continue to improve the outlook for women with pregnancy and diabetes.