The Influence of Prenatal Exercise Mode on Maternal Cortisol Levels during Pregnancy

Abstract

Background: Cortisol is essential for regulating metabolism, immune function, and stress response. During pregnancy, cortisol levels naturally rise to support fetal growth and development. However, elevated maternal cortisol levels are linked to adverse pregnancy outcomes, such as preeclampsia and preterm birth. While exercise is known to normalize cortisol levels in non-pregnant women, its impact during pregnancy remains unexplored. This study aims to examine the influence of different modes of exercise during pregnancy on maternal cortisol levels. Methods: This study consisted of women with singleton pregnancies, who were randomly assigned to one of four groups: aerobic (AE), resistance (RE), combination exercise (CE), or an attention control group (CON). Blood samples were collected at 16- and 36-weeks gestation to measure cortisol levels. Participant exercise sessions were supervised and tracked. Results: In all evaluated exercise types (AE, RE, and CE) the participants had normal levels of cortisol, normal birth outcomes, with no adverse pregnancy outcomes, and thus were deemed safe for pregnant women. The study observed different change patterns in cortisol levels from early to late pregnancy among exercising groups. At 16 weeks, all the maternal cortisol levels had a small effect size, which suggested the group values were similar. At 36 weeks, the AE and CE groups had a small effect size, which showed no difference between those values; but in the RE group, there was a large effect size, which showed a difference. The change scores of the maternal blood cortisol levels showed CON, RE, and CE groups increased from early to late pregnancy, however AE decreased from early to late pregnancy. Discussion: This study enhances the understanding of how exercise during pregnancy affects cortisol levels. While the RE group compared to the CON group showed a moderately strong increase at 36 weeks, this can be due to the large effect size. It provides insights into safe and beneficial exercise regimens, aiming to inform healthcare professionals and expecting mothers about the role of exercise in managing cortisol levels and promoting healthier pregnancy outcomes.