Natural Birth May Lead to Better Baby Bonding

Gennifer Tsoi | gennifer.tsoi@yale.edu February 26, 2009

Sample views of maternal brain activity for vaginal delivery (n=6) vs. Cesarean section delivery (n=6) for the contrast of own baby-cry vs. other baby-cry (p < .005). Areas of activity have been circled in black for easier visualization. Swain et al. (2008). Maternal brain response to own baby-cry is affected by cesarean section delivery. Adapted from Swain et al (2008), Fig 2.

The biological response for mothers to care for their young has sparked many studies in both animals and humans alike.

Research has been done to understand how humans transition from “non-parents” to parents, why some rodent mothers lick and groom their pups much more than others, and why a mother’s vigilant postpartum care can sometimes be considered an obsessive-compulsive disease.

Most recently, Yale Child Study Center Assistant Professor James Swain, M.D. has explored the “licking and grooming” phenomenon in humans. Swain, a clinician researcher who specializes in obsessive-compulsive disorder and Tourette’s disorder, recently published an article in the Journal of Child Psychology and Psychiatry examining the relationship between a mother’s bond to her baby and the method of delivery at birth.

Through interviews, self-reports, mood-ratings, specialized questions about parenting behaviors, and brain imaging fMRIs (functional magnetic resonance imaging), Swain and his fellow researchers discovered that vaginal delivery (VD) mothers are more sensitive to their own babies’ cries than cesarean section delivery (CSD) mothers are.

Studies of horses, sheep and rodents have shown that CSD causes an affiliative bond for a child to take longer to form. Oxytocin, nicknamed the “love hormone,” may prime a mother to bond with her baby.

However, this elusive hormone is very difficult to measure, as it requires blood samples and has too short of a half-life to allow meaningful analysis for this study.

Instead, Swain and his team opted to focus on brain imaging. Twelve healthy mothers in total were chosen for this cross-sectional study done here at Yale. Six voluntarily opted for CSD, none for medical reasons, and the other six chose VD.

Through fMRIs taken 2-4 weeks after birth, the researchers were able to tell that certain brain areas were more active in VD mothers when exposed to their own babies’ cries.

The front cortical areas, which deal with empathy and executive control, exhibited extra brain activity. Swain attributed this to emotions associated with mothers hearing their babies cry.

Deeper brain structures like the basal ganglia, which controls habitual and normal obsessive-compulsive behaviors, were also more active.

The cingulate cortex, the home of emotional regulation, also showed greater activity in VD mothers than in CSD mothers, leading to the conclusion that VD mothers had stronger responses to their own babies than CSD mothers.

While these are statistical, measurable differences, mothers have no reason to fear that CSD will severely impact their mothering abilities. Already, some evidence shows that the differences between VD mothers and CSD mothers decrease as the time after delivery increases.

Swain hopes that further studies can explore responses to baby pictures and cries well after the time of delivery. He hopes that partnering with the obstetrics and gynecology center might shed some light about prenatal factors that can affect mothers’ bonds with their babies.