Background: Physical activity has been hypothesized to reduce the risk of preeclampsia, but epidemiologic studies have not shown consistent results. Therefore, we conducted a systematic review and dose–response meta-analysis of epidemiologic studies.
Methods: PubMed, Embase, and Ovid databases were searched for case–control and cohort studies of physical activity and preeclampsia up to 2 November 2012. We estimated summary relative risks (RRs) using a random effects model.
Results: Fifteen studies were included. The summary RR for high versus low prepregnancy physical activity was 0.65 (95% confidence interval [CI] = 0.47–0.89, I2 = 0%; n = 5). In the dose–response analysis, the summary RR was 0.72 (0.53–0.99; I2 = 0%; n = 3) per 1 hour per day and 0.78 (0.63–0.96; I2 = 0%; n = 2) per 20 metabolic equivalent task (MET)-hours per week. The summary RR for high versus low physical activity in early pregnancy was 0.79 (0.70–0.91; I2 = 0%; n = 11). In the dose–response analysis, the summary RR per 1 hour per day was 0.83 (0.72–0.95; I2 = 21%; n = 7) and 0.85 (0.68–1.07; I2 = 69%; n = 3) per 20 MET-hours per week. A nonlinear association was observed for physical activity before pregnancy and risk of preeclampsia (test for nonlinearity, P = 0.03), but not for physical activity in early pregnancy (test for nonlinearity, P = 0.37), with a flattening of the curve at higher levels of activity. Both walking and greater intensity of physical activity were inversely associated with preeclampsia.
Conclusions: Our analysis suggests a reduced risk of preeclampsia with increasing levels of physical activity before pregnancy and during early pregnancy.