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How Becoming a Dad Changes Men

Less testosterone, and more oxytocin, if they step up.

Key points

  • Fathers who interact more often with their infants undergo more pronounced biological changes.
  • These biological changes help fathers become more sensitive caregivers and develop even closer emotional relationships with their infants.
  • It is important that new fathers are encouraged to become involved during pregnancy and to actively participate in infant care.

It is well known that, during pregnancy, women experience drastic hormonal and neural changes that are thought to prepare them for the physical, social, and emotional demands of pregnancy and motherhood. What may surprise many people is that biological changes are not only experienced by mothers; expectant fathers also undergo significant hormonal and neural alterations in the months leading up to and following childbirth.

Profoundly, the biological effects of fatherhood heavily depend on the extent that fathers are involved in caregiving, which has notably changed over the last several decades.

In 1970, fathers in the Western world spent approximately 12 to 25 minutes per day on child care (Roby, 1975); whereas, in 2010, Western fathers spent over an hour per day caring for their children (Craig & Mullan, 2010). Based on this data, contemporary fathers are about three to six times more involved in child care than the previous generation.

Various socio-cultural shifts have contributed to fathers spending more time caring for their children. For example, since the 1970s, programs like paid paternity leave have become increasingly common. As of 2022, 63% of the world’s countries guarantee fathers the opportunity to take paid paternity leave (Peck, 2023); however, many countries, including the United States, still do not guarantee leave for either parent, let alone fathers.

Programs like paid paternity leave fundamentally affect the amount of time fathers spend with their infants, which may have biological consequences. Researchers have found that fathers who are more involved in child care, particularly during early infancy, undergo more pronounced biological changes than fathers who are less involved—biological changes that can support men in being more compassionate caregivers, developing closer emotional relationships with their newborns, and becoming more attuned to their infants’ needs.

How Do Men's Hormones Change During the Transition to Fatherhood?

Less Testosterone Helps Men Prepare for Caregiving

During their partner's (or surrogate's) pregnancy, a man's body typically produces less testosterone—a hormone that contributes to muscle mass, sex drive, and aggressive impulses.

Researchers speculate that this decrease in testosterone leads to more caregiving behaviors during pregnancy and after childbirth. During pregnancy, reduced testosterone may lead expectant fathers to take better care of their pregnant counterparts, for example, by being physically gentle or creating comfortable places for their partners to rest. Nurturing behaviors like these ultimately protect the health and safety of the mother and fetus until the pregnancy is full-term. A similar effect occurs after childbirth: Fathers who undergo a more drastic reduction in their testosterone during pregnancy and immediately after delivery are more involved in infant care months later (Edelstein et al., 2017; Kuo et al., 2018).

Importantly, fathers who spend more time caring for their infants tend to have lower testosterone levels than other fathers (Meijer et al. 2019). Experts believe this is because the degree to which fathers’ testosterone levels decrease depends on how involved they are during pregnancy and after childbirth (Bakermans-Kranenburg et al., 2019).

More Oxytocin Helps Fathers Seek Physical and Emotional Closeness

Over the first six months following childbirth, men have elevated levels of oxytocin—a hormone that drives fathers to seek physical contact with their infants and helps fathers feel emotionally close to them.

Importantly, fathers’ bodies produce more oxytocin during play with their infants (Abraham & Feldman, 2018). This suggests that fathers who engage with their infants more often may form stronger emotional attachments to them and be more biologically inclined to engage with them later on.

Changes in Cortisol Help Men Identify Infant Distress and Provide Comfort

When fathers hear an infant crying (not necessarily their own), their bodies produce more cortisol (Fleming et al., 2002)—a hormone that is produced in stressful situations. These temporary peaks in cortisol help fathers rapidly detect and respond to infant distress.

Conversely, fathers’ cortisol decreases when they hold their infants or interact with their toddlers (Kuo et al., 2018; Storey et al., 2011). Researchers have theorized that repeatedly experiencing cortisol reduction following physical contact with their newborns reinforces attentive caregiving. In other words, fathers who more often seek physical closeness with their infants will be more inclined to seek physical closeness in the future, particularly after hearing their infant cry.

How Do Men's Brains Change During Fatherhood?

The Brain Gets Ready to Learn From Fatherhood

Researchers believe that leading up to the birth of their children, men’s brains become more plastic (Martínez-García et al., 2022). In other words, the structures, networks, and pathways in the brains of expectant fathers become less stable and are able to change more readily.

This means that fathers, compared to men without children, have a greater capacity to learn from their experiences because their experiences lead to consequential changes in the brain.

While quality time is important, the quantity of time fathers spend with their infants is crucial: Fathers who spend more time with their infants have more opportunities to learn from their caregiving experiences and, in turn, become more neurologically attuned to the needs, likes, dislikes, temperaments, and tendencies of their newborns.

Fatherhood Alters How the Brain Functions

When they hear an infant crying, both new mothers and new fathers show significantly more brain activity than non-parents in four important areas of the brain: the insula, precentral gyrus, postcentral gyrus, and right putamen (Witteman et al., 2019). These four brain regions work together to process sensory information (for example, the sight or sound of an infant crying) and initiate movement (for example, searching for and comforting the distressed infant). These functional changes in parents’ brains enable them to efficiently detect and react to their infants’ distress.

One study found that, under certain circumstances, brain activity in the amygdala (an area of the brain involved in emotional experience) and brain activity in the superior temporal sulcus (an area of the brain involved in social understanding) coincide more often in fathers who spend more time caring for their infants (Abraham et al., 2014). This supports the notion that fathers’ brains function differently depending on the amount of time they spend caring for their infants.

How Can We Support Father-Infant Interactions?

Because the degree to which fathers undergo constructive biological changes is based on the quality and quantity of their caregiving experiences, it is important that governments, medical institutions, and families support fathers in being more involved in child care.

Policymakers can encourage father involvement in infant care by instating or extending programs like paternity leave. Research indicates that the early interactions afforded by these programs are likely to result in more pronounced biological changes that lay the foundation for better father-child relationships.

Medical institutions can support father-infant interactions as early as pregnancy. For example, in a recent study, researchers encouraged expectant fathers to interact with their fetuses verbally or by softly massaging the mother’s abdomen wall (Buisman et al., 2022). The researchers used ultrasound to show both parents their baby’s responses, and video recordings of these sessions were reviewed by the father alongside a specialist who highlighted the father’s positive parenting behaviors.

Fathers who reviewed their interactions with a specialist were more sensitive during play with their babies after birth than fathers who did not. This suggests that interactions with feedback from a specialist can help fathers become more emotionally attached and more attuned to their infants.

Families can support father-infant interactions at home by making time for fathers to touch their partners’ abdomens, read a book aloud, or sing a lullaby.

The Takeaway

Although expectant fathers spontaneously undergo hormonal and neural changes in the months leading up to and following childbirth, those who are provided with (and take advantage of) opportunities to spend more time caring for their infants undergo further biological alterations. These more pronounced biological changes can support fathers in becoming more compassionate caregivers and developing closer emotional relationships with their children.

Hannah E. Marshall, a researcher at Yale University, contributed to the writing of this post.

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