Supportive co-parenting may help secure infant attachment development

UNIVERSITY PARK, Pa. — The World Health Organization recommends that babies should exclusively breastfeed for at least the first six months of their lives and continue alongside the introduction of other foods for at least two years, as breastmilk contains the nutrients and antibodies needed to help infants thrive. Beyond physical development, a new study from researchers in the Department of Human Development and Family Studies found that breastfeeding also had a positive impact on the mother’s parenting quality and, in turn, on the infant’s secure attachment to the mother. In addition, the study revealed that such secure attachment can also result from supportive co-parenting, regardless of whether the mother chose to breastfeed or not.

The findings were published in the Journal of Human Lactation.

“Breastfeeding incorporates both physical touch and the mother’s ability to be sensitive. A positive breastfeeding experience is important and has clear positive benefits for both the baby and the mother,” said Doug Teti, distinguished professor of human development and family studies and professor of psychology and pediatrics at Penn State and senior author on the paper. “Good quality support from partners is also beneficial in helping mothers bond with their infants, but our results show that partner support may be especially helpful to mothers who are unable or unwilling to breastfeed their infants.”

For this study, 167 mothers and their infants were recruited from two hospitals in Central Pennsylvania within 48 hours of the infants’ births. The families were visited in their homes at one, three, six, nine, 12 and 18 months, on multiple occasions at each timepoint. During these home visits, researchers observed the parents and children interacting at home as they normally would. Parents were also provided with video equipment to set up in the areas where the babies slept and instructed on how to record and document their infant’s bedtime routines and interactions.

These visits and videos allowed the researchers to assess the mother’s parenting quality, as well as whether the children had secure or insecure attachments to their mothers in their natural settings. Securely attached children explore the environment freely when they are content, but seek out the parent for comfort when faced with stressful or fear-inducing situations, like an unknown stranger visiting the home. Children with insecure attachments show an imbalance in these tendencies, either for the child to over-rely on the parent during times of low-stress, or to under-rely on the parent during times of high stress.

“Children with secure attachment have parents who are consistently sensitive and responsive to the child’s cues and needs, particularly in times of stress, and encourage the children to explore in times of low stress,” Teti said. “A good parent recognizes the need for both attachment and exploration when necessary and appropriate.”

The researchers also surveyed the mothers, asking them to report on their experience with breastfeeding, including how long they breastfed and on any co-parenting support they had.

A co-parent is any person the mother is partnering with to raise the child, whether a live-in romantic partner, biological relation or other live-in caregiver. Co-parenting refers to the coordination of parenting efforts between individuals involved in raising the child. Co-parenting can manifest in various ways in the household, including the levels of conflict in the home and how satisfied the parents are by the division of labor. For example, when co-parenting conflict is low and disagreements are limited — when parents are in agreement in how to set boundaries for the child and there is an equal division of labor — the overall quality of co-parenting is high.

Based on the in-home visits and surveys, the researchers found that breastfeeding appeared to have a clear, positive influence on mothers’ parenting quality and infants’ attachment. However, for those mothers who were unable to breastfeed for any number of reasons, the quality of co-parenting played a protective role. When the quality of co-parenting was high, mothers displayed higher quality parenting and infants had a secure attachment whether or not mothers breastfed their babies. When the quality of co-parenting was low, secure attachments primarily manifested when mothers breastfed their infants. In this way, the results highlighted the importance of positive co-parenting in situations where the mother does not or cannot breastfeed.

“Breastfeeding is one great way to promote secure attachment,” said Christine Kim, lead author on the paper who earned a doctorate in human development and family studies from Penn State in 2024. “But if a mother does not breastfeed, it is important to get the partner involved to have a strong support system. That, in turn, promotes good mother-infant bonding and secure attachment in the infant.”

The results of the study also have implications in a clinical setting, the researchers said.

“Pediatricians and early-life clinicians can support secure attachment, as well, by focusing on the whole family during conversations about infant health and breastfeeding,” Kim continued. “Our results suggest that it’s not just moms that matter — the spouse, partner or whoever is providing co-parenting support matters just as much. Ultimately, when parents work together, they provide more supportive parenting for the infant and more secure attachment for all.”

Kim is now a contract social science research analyst at the U.S. Department of Health and Human Services. Nicole Smith, a 2021 graduate of biobehavioral health with a minor in Human Development and Family Studies at Penn State, also contributed to this research. Members of Teti’s Study of Infants’ Emergent Sleep TrAjectories (SIESTA) research program were also involved.

The National Institutes of Health Funded this study and the Social Science Research Institute at Penn State funded a pilot study that led to this research.