Women who engage in light physical activity and lessen their sedentary time may significantly reduce the risk of key health problems during pregnancy, according to a new University of Iowa-led study.
Researchers examined the daily behaviors of 470 pregnant women across all stages of pregnancy. Each participant wore a monitor that measured physical activity in 24-hour cycles and another monitor that recorded the time they spent asleep.
Based on observational data collected from the study's participants, the researchers propose a "Goldilocks Day"-like guide for pregnant women that could reduce by nearly 30% the risk of developing hypertensive disorders of pregnancy (HDP), commonly occurring complications of pregnancy that include chronic hypertension, gestational hypertension, and preeclampsia.
Those recommendations are:
• Reduce sedentary time to fewer than eight hours each day.
• Engage in light physical activity for at least seven hours each day.
• Engage in approximately 22 minutes of moderate to vigorous physical activity, such as a brisk walk, each day.
• Get nearly nine hours of sleep each night.
Sedentary behavior is defined as being mostly inactive, such as sitting or lying down. Light physical activity can include myriad options, such as taking a casual walk, moving around the home, or simply standing.
"We are identifying the optimal composition of movement behaviors across the day associated with the lowest risk of developing HDP and the most improved health outcomes," says Kara Whitaker , associate professor in the Department of Health, Sport, and Human Physiology at Iowa and the study's corresponding author. "This blueprint holds for each and every trimester of pregnancy."
Study participants were enrolled at study sites in Iowa City, Iowa; Pittsburgh; and Morgantown, West Virginia. The women, 4 in 5 of whom were non-Hispanic white and nearly a quarter of whom were rural residents, wore the activity and sleep monitors for at least a week during each trimester of pregnancy.
The data showed a steep increase in HDP risk for pregnant women who were sedentary for more than 10 hours per day. Conversely, pregnant women who upped their light physical activity to at least four hours per day reduced their HDP risk to 15% from 30%.
"Just moving around more seems to have significant health benefits," Whitaker says, "and I think it also may be a more feasible target for women who are pregnant who are not exercising regularly."
The researchers were surprised to find out that participants who engaged in moderate to vigorous physical activity showed no appreciable benefit from longer durations, while sleep beyond a certain duration also yielded no major benefits.
"Through this study, we are providing evidence that reducing sedentary behavior and engaging in light physical activity are important, and maybe more important, when it comes to pregnancy and health," Whitaker says.
Knowing which mix of behaviors has the greatest impact on women's health in pregnancy is important, Whitaker notes, because clinical research has shown that women who develop HDP are more than twice as likely to develop heart disease later in life.
"We know that cardiovascular disease is the number one killer of women, and if we can intervene in pregnancy and prevent women from developing a hypertensive disorder of pregnancy, we are putting them on a better trajectory, away from cardiovascular disease and toward more optimal cardiovascular health," she says.
The study, "Optimal 24-hour movement behaviour compositions across trimesters and risk of hypertensive disorders of pregnancy: the Pregnancy 24/7 cohort study," was published online June 10 in the British Journal of Sports Medicine.
The findings complement a second study, published online May 27 in the Journal of the American Medical Association, that looked more in depth at the ratio and type of sedentary behavior and light physical activity for the best mix of behaviors to lessen HDP risk. Whitaker is a lead co-author on that study.
Co-authors in the British journal's study are Alex Crisp, Jaemyung Kim, Karina Smith, Donna Santillan, Mark Santillan, and Bridget Zimmerman, from Iowa; Jacob Gallagher, from Iowa State University; Melissa Jones, from Oakland University in Michigan; Bethany Barone Gibbs, Katrina Wilhite, Alexis Thrower, and Iqra Sheikh, from West Virginia University; and Sabera Rahman, Janet Catov, Christopher Kline, and Maisa Feghali, from the University of Pittsburgh.
The National Institutes of Health, the University of Iowa Institute for Clinical and Translational Science, the University of Pittsburgh Clinical and Translational Science Institute, and the West Virginia Clinical and Translational Science Institute funded the research.
