Determinants of cortisol during pregnancy - The ABCD cohort

Psychosocial stress during pregnancy has been proposed as a major contributor of glucocorticoid-mediated programming of the fetal hypothalamic-pituitary adrenal (HPA) axis, with later adverse health consequences. However, evidence linking maternal stress to maternal cortisol values during pregnancy is inconclusive. A possible explanation for this is that other maternal factors overshadow any potential effects of stress on cortisol levels. We studied a large cohort of pregnant women with extensive data on pregnancy characteristics to determine the respective contributions of biological, environmental and psychosocial stress factors to cortisol levels in pregnancy.

We used data from 3039 women from the Amsterdam Born Children and their Development-study cohort. Serum cortisol was measured in blood, collected at the first prenatal visit, at different gestational ages (median=91days, range=40-256days), and at various time points during the day (median=11:45h, range=08:00-18:30h). We assessed associations between maternal serum cortisol in pregnancy and biological factors, lifestyle factors and stress factors, including depression, anxiety, pregnancy-related anxiety, work stress, parenting stress and fatigue.

In multivariable analysis, variables that were associated with higher cortisol levels in pregnancy were lower maternal age [1.5nmol/l, 95%CI (0.6-2.4)], being nulliparous [21.5 nmol/l (15.9-27.1)], lower pre-pregnancy body mass index (BMI) [1.3nmol/l (0.3-2.4)], higher C-reactive protein (CRP) [1.0nmol/l (0.4-1.5)], carrying a female fetus [9.2nmol/l (1.8-16.5)], non-smoking [14.2nmol/l (0.6-27.7)], sufficient sleep [8.5nmol/l (0.9-16.1)], and being unemployed [12.7nmol/l (2.2-23.2)]. None of the psychosocial stressors was significantly associated with serum cortisol levels in pregnancy. A total of 32% of all variance in cortisol was explained by gestational age, maternal age, time of day, parity, pre-pregnancy BMI, CRP, fetal sex, smoking behavior, self-reported sleep sufficiency, and employment.

Our data suggest that maternal cortisol during pregnancy is mainly affected by biological and lifestyle factors, but not by psychosocial factors. We suggest that psychosocial stress in pregnancy might program the fetus through other mechanisms than through altering maternal cortisol levels.