Uncontrolled Diabetes Leads to More Birth Defects

Better get your blood glucose under control before you even think about getting pregnant.

Researchers in Texas studied 145,196 women who delivered babies between January 1, 1991, and December 31, 2000, to determine whether the women had diabetes before pregnancy or developed gestational diabetes.

Women who had diabetes before they got pregnant or who developed gestational diabetes with elevated fasting blood-glucose levels were three to four times more likely to have babies with birth defects than women who either did not have diabetes before pregnancy or who developed what researchers termed “mild” gestational diabetes. “Mild” gestational diabetes was defined as diabetes that did not require insulin injections to control glucose levels.

Birth defects occurred in 1.5 percent of women who did not have diabetes, in 1.2 percent of women who had “mild” gestational diabetes with normal fasting blood glucose, in 4.8 percent of women who had gestational diabetes with elevated fasting blood glucose of 105 mg/dl or greater and in 6.1 percent of those who had diabetes before getting pregnant.

As the lead researcher noted, however, previous studies have shown that tight blood-glucose control before and during pregnancy helps to lower the risk of having a baby with birth defects.

—Obstetrics & Gynecology, November 2002

Clinical adviser’s note: It is well-recognized that elevated blood-glucose levels during the first trimester of pregnancy, the time of fetal organ development, can result in birth defects and spontaneous abortions. This research report raises this question: how many of these women had undiagnosed type 2 diabetes at the start of their pregnancy, putting their babies at risk for birth defects? Regular diabetes screening for women of childbearing potential who have risk factors for diabetes seems important.

For women already diagnosed with diabetes, this study is a reminder of the importance of pre-pregnancy counseling to achieve optimal glucose control and changes to safe medications during pregnancy.

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