Fathers who are sleep-deprived thanks to their first babies may have trouble conceiving their next children. That’s largely the fault of the brain’s pineal gland—which is in charge of both regulating sleep and releasing reproductive hormones such as testosterone. So when your sleep is screwed up, there can be quite the domino effect.
“That disruption in taking care of yourself because of the first baby can contribute to issues of not being able to conceive the second baby,” Jane Frederick, a fertility reproductive endocrinologist, told Fatherly.
One study of 953 Danish men, published in the American Journal of Epidemiology, found that men who reported the most sleep disturbances experienced the lowest sperm counts, and were more likely to have mutated swimmers. Indeed, sleep deprivation has even been shown to prevent male rats from reproducing normally. And lack of sleep doesn’t merely damage the male reproductive system. Research suggests that sleep deprivation affects a woman’s ability to conceive as well, further stacking the deck against tired parents trying to get pregnant again. It may even be worse for women, Frederick says, because they’re more likely to suffer from insomnia to begin with.
“In both men and women, we know that the same part of the brain regulates sleep and wake hormones,” Frederick says. “If you’re concerned about your fertility and not getting enough sleep, it may be that those sleep hormones are not allowing the release of your reproductive hormones.”
Not that lack of sleep is the only problem. Frederick says it’s also important to eat right and exercise, and she also cites preliminary research that suggests men who get too much sleep also may have fertility troubles. The sweet spot seems to be between seven and eight hours—often an impossibility until your child is about two years old. And that’s convenient, because Frederick suggests parents resist trying again until their first child is around two years old, anyway. By that time, the everyone will be better equipped for the transition, including kid number one.
“Spacing out the children in your family will help you take better care of yourself,” she says. “And allow that first child to separate more easily so you can focus on the second one.”