Updated: Jul 18
We often hear about the effects of pregnancy and parenting on women’s bodies and brains— hence the proverbial “mum brain”. But did you know that men go through hormonal and brain changes as well? While these changes are not as well researched as those of pregnant and new mothers, these changes are thought to “prime” dads for caring for a new baby.
So what happens to dads during pregnancy?
1. Testosterone Drops
One of the most consistent findings in studies on expectant and new fathers was that dads had lower levels of testosterone than non-dads. Testosterone is the main sex hormone in males and is involved in fertility and maintenance of muscle mass. Testosterone levels are shown to vary depending on the type of relationship men are in—men in long-term relationships are shown to have lower levels than those who are single or are in new relationships. The transition to parenthood is also associated with testosterone drops, dads of newborn babies having testosterone levels up to 33% lower than expectant dads. These lower levels of testosterone are thought to be linked with dads bonding and caring for their newborn. A longitudinal study found that dads involved in childcare had lower levels of testosterone compared to those that were not involved. We assure you that this drop in testosterone does not indicate that dads are less “manly”—in fact, it makes them better fathers!
Becoming better fathers: testosterone is associated with greater bonding and nurturing.
2. Cortisol May Increase
In the same study that found decreased testosterone levels, cortisol levels of fathers were found to rise during late pregnancy and labour. It is important to note that other studies found that cortisol levels do not change in new dads. These differences may be due to the time that cortisol was measured as well as differences in measurement techniques. Cortisol is a key stress hormone in both males and females, and higher levels in dads on the very day that their child is born might be linked to greater future involvement in infant care and play. However, higher levels of cortisol in dads six weeks after birth is shown to have the opposite effect in caregiving (they are likely to be less involved when it’s high).
3. Other Hormonal Changes
A study has found that estradiol also increases in fathers-to-be. While estradiol is key for maternal behaviours in women, not much is known about the effects of estradiol on fathering. It also should be noted that—like cortisol—results for estradiol changes vary, with many studies finding that estradiol actually declines in men during pregnancy.
Prolactin may also rise during pregnancy, with levels at its peak in new dads. While this hormone is linked with milk production in women, higher levels of prolactin in men were linked to greater reactivity to their newborn’s cries.
Prolactin and other hormones help dad become more responsive to their newborn.
4. Structural Changes in the Brain
Along with the changes in hormone levels, fathers were also seen to experience changes in their brain. These changes are similar to those found in new moms with increases in areas for nurturing and empathy. For example, there is an increase in grey matter—or the outermost layer of the brain—in areas for attachment and response for the baby after birth. Increases in the grey matter shows more use of that particular area of the brain and are thought to indicate the brain acquiring parenting skills.
Image taken from Kim et al. (2014). The brain goes through structural changes to prepare for childcare—grey matter increases (orange) and decreases (blue) in dad’s brains from 2–4 weeks to 12–16 weeks after the baby is born.
What does this mean for new dads?
As you are becoming a parent, you are going through massive changes. It is important to remember that these hormonal and brain changes are normal and help you prepare for your new role as a dad. Becoming a parent is a huge transition so be compassionate towards yourself and give yourself time to adjust to your new role. It’s amazing to think that in the future we would have a better understanding of the full effect of the changes that dads go through at the start of fatherhood.
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