Context: The underlying biological mechanisms of stress-related pregnancy complications in humans are still poorly understood. Recent research on pharmacological or physical provocation procedures in pregnant women has resulted in inhomogeneous findings. Furthermore, no studies conducted so far have employed a psychosocial stress paradigm at different stages of pregnancy.

Objective: To identify endocrine, autonomic and psychological responses to standardized psychosocial stress at different stages of pregnancy.

Design: Ninety healthy women (aged 21 - 37 yr), including thirty pregnant women at the beginning of the second trimester and thirty women at the beginning of the third trimester, as well as thirty non-pregnant women in the follicular phase of their menstrual cycle, underwent a psychosocial stress test. Salivary free cortisol, -amylase, heart rate, and psychological parameters were repeatedly measured.

Results: Salivary cortisol recovery was significantly prolonged in second-trimester pregnant women (P = 0.04). Cortisol and heart rate increases of both pregnant groups were shown to be comparable with those of the controls. -amylase increases of both pregnant groups were markedly attenuated compared with non-pregnant women (P = 0.008).

Conclusions: From these data, we conclude that in contrast to pregnancy in rats, pregnancy in women does not result in a restraint of the hypothalamic-pituitary-adrenal axis to psychosocial stress. Furthermore, attenuated -amylase stress response might reflect protective processes within the autonomic nervous system during pregnancy, whereas prolonged cortisol recovery during the beginning of second-trimester pregnancy might be associated with the vulnerability to stress-related pregnancy complications during this period of time.