Glucose metabolism during pregnancy plays a pivotal role in maternal and fetal health. Impaired glucose tolerance in pregnancy, such as gestational diabetes, is at the center of the “diabetes begetting diabetes” intergeneration vicious circle. It has been related to not only adverse obstetrics and perinatal outcomes, but also substantially increased risk of cardiometabolic disorders in both mothers and their children over their life span. A large portion of childhood obesity and pediatric type 2 diabetes may be explained by intrauterine exposure to gestational diabetes. As such, it is important to identify modifiable risk factors for the improvement of glucose metabolism in pregnancy and for the prevention of gestational diabetes. Among women with gestational diabetes, physical activity has been demonstrated to improve glycemic control and decrease the need for insulin therapy. However, from a prevention perspective, it remains unclear whether the time physical activity is performed (e.g., before and/or during pregnancy and longitudinal trajectory) is related to glucose metabolism in pregnancy and the risk of gestational diabetes.
Our study, published in the December issue of Medicine & Science in Sports & Exercise®, sought to address the physical activity timing question. The study population consisted of 2,388 women from the National Institute of Child Health and Human Development Fetal Growth Studies–Singletons. Physical activity data was collected at each study visit using the Pregnancy Physical Activity Questionnaire. This is a semi-quantitative questionnaire validated for pregnancy. Reported sports/exercise activity types and duration were used to determine levels of weekly moderate and vigorous physical activity. Women were asked to recall types and duration of their physical activity during the periconception period (past 12 months, inclusive of first trimester), 13 to 20 weeks of gestation and 20 to 29 weeks. Glucose challenge and oral glucose tolerance test results were abstracted from the medical record. Gestational diabetes was diagnosed using the Carpenter and Coustan criteria.
The key take-away from this study was that both the timing and the dose of physical activity were related to glucose metabolism during pregnancy. High levels of moderate and/or vigorous physical activity (=75th percentile; =760.5 MET·min·week-1) in the early-to-mid and mid-to-late second trimester were associated with lower glucose concentrations. Further, pregnant women who maintained levels of moderate and/or vigorous physical activity as recommended by the American College of Obstetricians and Gynecologists (500 MET ·min·week-1) from pre-pregnancy through the second trimester had significantly lower glucose concentrations.
Taken together, our study demonstrated that participation in higher levels of moderate and/or vigorous physical activity in early-to-mid second trimester of pregnancy elicits improved glucose metabolism. Our findings also highlight the importance of persistently engaging in an active lifestyle from preconception period throughout pregnancy. Yet, the remaining critical questions are 1) how to translate these findings into practice to guide pregnant women or women who are planning pregnancy and 2) what specific physical activity programs are accessible, safe and time-efficient for pregnant women to improve cardiometabolic health. Future endeavors along these lines are clearly warranted.
Cuilin Zhang, M.D., Ph.D., M.P.H., is a senior investigator with tenure in the Division of Population Health Research at the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health. She is also an adjunct professor in the Department of Population, Family and Reproductive Health at Johns Hopkins University. Dr. Zhang leads a transdisciplinary research program designed within a life course health paradigm so that the etiology and prevention of complex diseases may be investigated during multiple critical time windows over life plan and across generations. Her research has focused on nutrition and lifestyle, metabolic and genetic determinants, as well as health consequences of gestational diabetes, type 2 diabetes, obesity and related comorbidities.
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