In a series of studies from our group, we have shown that fetuses of mothers experiencing psychological distress also show significantly different reactivity to acute maternal stress. Fetuses of depressed mothers showed a significantly higher increase in FHR when the mother was introduced to a lab-induced stressor [21]. Similar increases in FHR were found in fetuses of anxious and anxiodepressive comorbid women [22–24]. In these studies, there were no group differences in baseline FHR, or in women’s cardiorespiratory reactivity to the laboratory challenge, which demonstrated significant increases. We interpret these results as indicating that fetuses have group differences in their acute reactivity to changes in the intrauterine environment, that is, to changes in maternal heart rate, respiration, and blood pressure, which may function as auditory and kinesthetic stimuli to the fetus and thereby reveal variation in fetuses’ central nervous system development. In a similar study of pregnant women exposed to a laboratory–based stressor, DiPietro et al, found increased FHR variability (which usually is associated with lowered FHR) and reduced movement during the challenge period compared to baseline [25]. The contrasting results between our