Pregnancy May Permanently Rewire the Brain, Study Says

A study on pregnant mice reflects the changes that happens in a pregnant human’s brain — and could help us understand postpartum depression

Hormonal changes in pregnancy lead to permanent changes in a mother’s brain, according to a new study on mice that reflects how similar changes happen in humans.

The study, carried out by London’s Francis Crick Institute and published in Science, found that changes in progesterone and estrogen triggered parental behaviors in mice.

By using tiny devices attached to the mice's heads, scientists were able to track neurons in the hypothalamus, the part of the brain considered to “regulate parental behaviors,” according to the National Institute of Health.

Mice mothers spent their time looking after their young, while “virgin” mice showed no interest in the babies, the study said.

“We think that these changes, often referred to as ‘baby brain’, cause a change in priority – virgin mice focus on mating, so [they] don’t need to respond to other females’ pups, whereas mothers need to perform robust parental behavior to ensure pup survival,” Dr. Jonny Kohl, who led the research at London’s Francis Crick Institute, told The Guardian.

“What’s fascinating is that this switch doesn’t happen at birth – the brain is preparing much earlier for this big life change.”

Human mothers experience changes to their brain as well, as pregnancy can impact the brain for up to two years, according to a report in Science: “New mothers' brains are more efficiently wired in areas that allow them, for instance, to respond to their infant's needs or to detect threatening people in their environments.”

Related: Breastfeeding May Help Improve Mothers' Brains Long-Term, Study Finds

While “baby brain” can be seen as a derogatory thing, with new mothers being pegged as “forgetful” or “absentminded,” according to a study reported in Salon, new mothers actually saw an increase in gray matter in areas of the brain that dealt with multitasking, empathy, and social cognition.

“We know that the female body changes during pregnancy to prepare for bringing up young. One example is the production of milk, which starts long before giving birth,” Dr. Kohl told The Guardian. “Our research shows that such preparations are taking place in the brain, too,”

“There is still so much we don’t understand about parenting and hormone signaling in the body and brain – these results are a solid step in that direction,” Prof. Robert Froemke, of NYU Langone told The Guardian.

“Parenting is among the most complex and difficult set of behaviors we and other animals engage in, and there’s not a lot of room for ‘trial and error’ especially in the earliest days of postpartum when infants need a lot of care.”

Understanding what happens to the brain is essential for postnatal care for the mother as well, since postpartum depression has been linked to hormonal changes in the brain.

“When you are pregnant, levels of the female hormones estrogen and progesterone are the highest they’ll ever be. In the first 24 hours after childbirth, hormone levels quickly drop back to normal, pre-pregnancy levels,” reports the Office on Women’s Health .

Related: Stars Who've Opened Up About Their Struggles with Postpartum Depression

“Researchers think this sudden change in hormone levels may lead to depression.”

And the National Institute of Health notes that “progesterone is the most abundant hormone in pregnancy. The dramatic drop in progesterone after birth may have a role in postpartum depression,” adding, “Further research on hormonal adjuvant therapy is needed.”

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