Beyond the HPA-axis: Exploring maternal prenatal influences on birth outcomes and stress reactivity

Accumulating evidence suggests that antenatal maternal stress is associated with altered behavioral and physiological outcomes in the offspring, however, whether this association is causal and the underlying biological mechanisms remain largely unknown. While the most studied mediator of maternal stress influences on the fetus has generally been cortisol, alternative novel markers of stress or inflammation warrant further consideration. The current investigation explored the influence of variations in self-reported symptoms of distress, stress hormones and inflammatory markers on infant birth outcomes and early stress regulation. The sample consisted of 104 pregnant women (mean gestational age = 34.76; SD = 1.12) and their healthy newborns. Maternal self-reported symptoms of depression and anxiety were evaluated through the Edinburgh Postnatal Depression Scale and the State-Trait Anxiety Inventory and levels of serum Interleukine-6 (IL-6), C-Reactive Protein (CRP), salivary cortisol and alpha amylase (sAA) were measured in late pregnancy. Newborns' cortisol and behavioral response to the heel-stick was assessed 48-72 hours after birth. The associations between maternal stress measures and infant birth outcomes and stress reactivity, adjusted for potential confounders, were examined through hierarchical linear regressions and hierarchical linear models. Higher maternal IL-6 levels were associated with smaller head circumference at birth, while diurnal sAA levels were positively associated with birthweight. Maternal diurnal cortisol was related to newborn's stress reactivity: a flatter infant cortisol response to the heel-stick was associated with greater maternal cortisol increases after awakening during pregnancy, while greater infant behavioural reactivity was related to a flatter maternal diurnal cortisol profile. The observational nature of these data does not allow for causal inferences but the current findings illustrate that antenatal factors related to alterations in maternal stress and immune response systems are associated with fetal growth and neonatal stress reactivity. This may have implications for later health and psychological outcomes.