Pre-pregnancy obesity and maternal circadian cortisol regulation: Moderation by gestational weight gain

Abstract

We investigated main and interactive effects of maternal pre-pregnancy obesity and gestational weight gain on circadian cortisol from the second to third trimester. A diverse sample of 215 pregnant women was enrolled. Maternal height and most recent pre-pregnancy weight were collected at study initiation (22% obese). Weight and circadian salivary cortisol samples were measured during second (24±4) and third (35±1 weeks) trimesters. During the third trimester, women who were obese prior to conception showed elevated evening cortisol versus normal weight women. This pattern was moderated by weight gain in excess of Institute of Medicine guidelines, such that women who were obese prior to conception and gained greater than 7.94kg by the 35±1 week visit displayed greatest elevations in evening cortisol. Given links between excessive prenatal glucocorticoid exposure and both poor maternal and offspring health outcomes, elevated maternal cortisol may be one mechanism underlying links between maternal obesity and adverse perinatal outcomes.

Keywords: Cortisol; Glucocorticoid; Obesity; Pregnancy; Weight gain.

Figure 1

Evening cortisol patterns differ by pre-pregnancy obesity group in late pregnancy. Post-hoc analyses demonstrated that women who were obese prior to pregnancy (n=38) had higher evening cortisol values than women who were not obese prior to pregnancy (n=107) at 35±1 weeks gestation. There were no significant differences in cortisol values between women who were obese prior to pregnancy (n=33) and women who were not obese prior to pregnancy (n=118) at 24±4 weeks gestation.

Figure 2

Excessive weight gain (>7.94kg) in women obese prior to pregnancy leads to elevated evening cortisol at 35±1 weeks gestation. The above results derived from a Repeated-Measures ANOVA suggesting that for women who were obese prior to pregnancy, excessive weight gain (n=22) led to elevated evening cortisol, though this pattern was not observed for obese women gaining within IOM recommendations (n=10). Further, there were no differences in circadian cortisol among women who were not obese prior to pregnancy, regardless of whether they gained within (n=45) or above IOM guidelines (n=41). IOM Guidelines were adjusted for 35 weeks gestation duration such that excessive weight gain was defined as >14kg in women of normative weight prior to pregnancy, >10.26kg in women who were overweight prior to pregnancy, and >7.94kg in women who were obese prior to pregnancy.