A more effective, but methodologically challenging, way to evaluate whether maternal psychological state affects the developing fetus is to manipulate maternal state and observe whether there is a fetal response. Maternal challenge using the Stroop color–word task was associated with increased variability in fetal heart rate and suppression of motor activity, with return to baseline levels at termination of the stressor. We have also used maternal viewing of a labor and delivery documentary as a maternal manipulation; fetuses responded with decreased motor activity and, in contrast to the Stroop intervention, also with decreased heart rate variability. Analysis of the fetal response to a specific component of the documentary—the first graphic birth scene—revealed a somewhat different pattern of responsiveness. Fetuses of women who had not given birth before showed a transient increase in motor activity during this scene. Reactivity and regulation are core constructs of temperament and important characteristics of child behavior. We have reported moderate stability over gestation in the degree of both the maternal physiological response and the degree of fetal reactivity and prediction to response patterns in infancy from response patterns in the fetus. Together these suggest that maternal reactivity to stressors may serve to entrain the developing fetal response