Does physical activity during pregnancy reduce the risk of gestational diabetes among previously inactive women?

Background: Gestational diabetes affects approximately 7 percent of all pregnancies in the United States; its prevalence may have increased among all ethnic groups since the early 1990s. Our study examined whether physical activity during pregnancy reduced the risk of gestational diabetes among women who were physically inactive before pregnancy. Methods: We used data from the 1988 National Maternal and Infant Health Survey (NMIHS), a nationally representative sample of mothers with live births. The NMIHS obtained mothers' gestational diabetes diagnoses from care providers and mothers reported their physical activity before and during pregnancy, including the number of months with physical activity and types of physical activity. We developed a physical activity index, the product of the number of months with physical activity, and average metabolic equivalents for specific activities. The analysis included 4,813 women who reported being physically inactive before pregnancy, with singleton births and no previous diabetes diagnosis. Results: Gestational diabetes was diagnosed in 3.5 percent of the weighted sample in 1988. About 11.8 percent of these previously inactive women began physical activity during pregnancy. Women who became physically active had 57 percent lower adjusted odds of developing gestational diabetes than those who remained inactive (OR 0.43, 95% CI 0.20-0.93). Women who had done brisk walking during pregnancy had a lower adjusted risk of gestational diabetes (OR 0.44, CI 0.19-1.02) and women with a physical activity index score above the median had 62 percent lower odds of developing gestational diabetes than the inactive women (CI 0.15-0.96). Conclusions: Results suggest that physical activity during pregnancy is associated with lower risk for gestational diabetes among previously inactive women.