Why Fatherhood Means Less Sex

A new study finds that becoming a dad lowers one’s testosterone level

Is there any truth in the belief that couples have less sex after the birth of a baby? Does the female partner become less attractive to the male, as is often suggested, or does parenthood have a biological impact on the father, just like the mother?

A new study has found that when men become fathers, they experience a sharp decline—usually about one- third—in their testosterone levels. But if the male is an involved parent, actively participating in childcare, it plummets by another 20 per cent.

For the research, 433 young men in the Philippines were studied. Their testosterone levels were first tested when they were 21 years old and single. Five years later, they were retested when they had turned 26 and become fathers. They found that these men were having less sex. There was also at least a one-third decline in their testosterone levels.

The researchers argue that this drastic dip in testosterone levels is caused by a natural impulse to protect and care for the newborn. Less testosterone, they say, ensures that the male is less aggressive and more caring. Arguing that men are biologically hardwired to focus on childcare at the expense of their sex drive, Lee Gettler, the lead researcher from University of Notre Dame in Indiana, UK, told The Guardian, “If their testosterone goes down, the men might be more oriented towards their family’s needs and not getting into conflicts with other men or looking for new mates.”

The researchers also found an increase in the hormone prolactin in new fathers, especially among those actively participating in childcare. This hormone is usually associated with breastfeeding, and, according to the researchers, this also causes men to be more responsive to their children’s needs. Gettler told The Telegraph, “We found that men who became new fathers had a decline of testosterone of between 33-34 per cent. Men who were most involved in day-to-day hands-on childcare had the lowest testosterone levels. If you think about fathers in other mammalian species, they don’t really help taking care of the children. So it seems that natural selection has stepped up men’s hormone systems to respond to the needs of their offspring.”

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