Maternal early pregnancy body mass index and diurnal salivary cortisol in young adult offspring.

Background Maternal early pregnancy overweight (body mass index [BMI] 25.0-29.9 kg/m2 ) and obesity (BMI ≥ 30 kg/m2 ) are associated with mental and physical health adversities in the offspring. Prenatal programming of the hypothalamic-pituitary-adrenal (HPA) axis has been put forward as one of the mechanisms that may play pathophysiological role. However, evidence linking maternal overweight and obesity with offspring HPA-axis activity is scarce. We studied if maternal early pregnancy BMI is associated with diurnal salivary cortisol, a marker of HPA-axis activity, in young adult offspring. Methods At a mean age of 25.3 (standard deviation [SD) = 0.6) years, 653 Arvo Ylppö Longitudinal Study participants collected saliva samples for cortisol analyses, at awakening, 15 and 30 min thereafter, 10:30AM, 12:00PM, 5:30PM and at bedtime. Maternal BMI was calculated from weight and height verified by a measurement in the first antenatal clinic visit before 12 weeks of gestation derived from healthcare records. Results Per each one kg/m2 higher maternal early pregnancy BMI offspring diurnal average salivary cortisol was -1.4% (95% CI:-2.6, -0.2, pFDR  = 0.033) lower, at awakening it was -2.4% (95% CI:-4.0, -0.7, pFDR  = 0.025) lower and the morning average salivary cortisol was -2.0% (95% CI:-3.4, -0.5, pFDR =0.017) lower. These associations were independent of the offspring's own young adulthood BMI, and other important covariates. Conclusion Our findings show that young adult offspring born to mothers with higher early pregnancy BMI show lower average levels of diurnal cortisol, especially in the morning. Whether these findings reflect prenatal programming of the offspring HPA-axis activity warrants further investigation.