Exposure Analysis Methods Impact Associations Between Maternal Physical Activity and Cesarean Delivery

Abstract

Background Previous studies report conflicting results regarding a possible association between maternal physical activity (PA) and cesarean delivery. Methods 7-day PA recalls were collected by telephone from n=1205 pregnant women from North Carolina, without prior cesarean, during two time windows: 17-22 weeks and 27-30 weeks completed gestation. PA was treated as a continuous, non-linear variable in binomial regressions (log-link function); models controlled for primiparity, maternal contraindications to exercise, pre-eclampsia, pregravid BMI, and percent poverty. We examined both total PA and moderate-to-vigorous PA (MVPA) at each time. Outcomes data came from medical records. Results The dose-response curves between PA or MVPA and cesarean risk at 17-22 weeks followed an inverse J-shape, but at 27-30 weeks the curves reversed and were J-shaped. However, only (total) PA at 27-30 weeks was strongly associated with cesarean risk; this association was attenuated when women reporting large volumes of PA (>97.5th percentile) were excluded. Conclusion We did not find evidence of an association between physical activity and cesarean birth. We did, however, find evidence that associations between PA and risk of cesarean may be non-linear and dependent on gestational age at time of exposure, limiting the accuracy of analyses that collapse maternal PA into categories.

Current Resources for Evidence-Based Practice, September 2020

“…Importantly, I was still able to present the findings that physical activity did not correlate with cesarean birth in our sample. These findings were just now couched within a larger discussion of how to analyze data on physical activity during pregnancy instead of within a discussion on whether physical activity could prevent cesareans ( Bovbjerg et al., 2015 ). Lest I portray myself as some paragon of publishing virtue, I’ll admit the other paper that stemmed from my dissertation also did not contain exciting results, and when faced with the huge amount of work to redo it, I availed myself of Option 1.…”