Research on stress provocation in pregnant women has resulted in inhomogeneous findings regarding the alterations of the hypothalamus-pituitary-adrenal (HPA) axis and the autonomic nervous system (ANS) with respect to the ongoing pregnancy and the type of stressor. In a series of studies we examined the endocrine and autonomic responses to (a) standardized psychosocial stress at different stages of pregnancy and (b) to an invasive diagnostic procedure (amniocentesis) during the 2nd trimester.
In study 1 we exposed 30 healthy pregnant women at the beginning of the 2nd trimester (group 1), 30 healthy pregnant women at the beginning of the 3rd trimester (group 2) and 30 healthy non-pregnant controls (group 3) to a standardized psychosocial stress test. In study 2 healthy pregnant women (n=34) underwent amniocentesis for karyotyping. Stress response was measured by endocrine parameters from saliva samples (cortisol (F), cortisone (E), and alpha-amylase) and heart rate for the calculation of the heart rate variability (HRV). In study 2 E/F ratio was assessed from amniotic fluid samples, additionally. In study 1 stimulated SAM and HPA response showed sig. increases in group 1 and 3 following stress exposure, but blunted responses in the second group. In study 2, the amniocentesis provoked a sig. increase of the SAM parameters. Baseline HRV indices, mirroring autonomic sympatho-vagal balance, were negatively correlated with amniotic fluid E/F ratio and positively with F, whereas a stronger HRV stress response was positively related to E/F ratio and negatively to F.
Our data provide evidence that (a) healthy pregnant women show characteristic stress responses during pregnancy and (b) allostatic processes seem to be initiated to counterbalance the effects of acute stress.