Methods: HRV data were continuously collected using MindWare 3000A Wireless System during a stressful parenting task where each expecting parent was individually exposed to a 10 minutes of crying from a lifelike baby doll and asked to “take care of the baby as if it were your own.” RMSSD, which measures beat-to-beat variability and provides a measure of autonomic nervous system arousal, was used in these analyses. The data were grouped into 30-second intervals and then averaged for each epoch to create a baseline, baby cry and recovery score. Multilevel mixed-effects models were estimated in Stata/MP 16 and included an interaction term to evaluate sex differences in physiological responses to the protocol.
Results: The level (intercept) and shape (slope) of the data were markedly different for expectant mothers versus fathers. Mothers demonstrated lower HRV across the entire protocol, compared to fathers. Although their intercepts were different, HRV decreased at approximately the same rate for mothers and fathers at the beginning of the protocol. However, mothers’ HRV began to increase more rapidly as the protocol continued - the slope for mothers increased at a statistically significant rate shortly after the protocol began (B = 0.11, p<0.001), and then leveled off. Fathers, in contrast, demonstrated lower HRV levels for a longer period during the protocol. However, rather than plateauing, fathers HRV increased rapidly toward the end of the protocol ((B = 0.08, p<0.001) and continued to increase during the recovery period.
Conclusion and Implications: Findings suggest that risk-exposed mothers and fathers may mount different physiological responses when exposed to infant crying. Mothers adapted physiologically to the protocol more quickly than fathers, suggesting that they were able to calm down fairly quickly once they engaged in soothing behaviors to calm the baby doll. Fathers, in contrast, became more physiologically activated throughout the protocol, suggesting that that they may have felt less confident in their soothing efforts. These findings inform the development of social work interventions that take a differential approach to work with expectant mothers and fathers. Whereas, mothers may benefit from support and encouragement, fathers may benefit from an educational approach that teaches effective soothing techniques.