Pregnancy has surprising effects on brain remodeling revealed

According to new findings by scientists, pregnancy leads to permanent restructuring of the brain. Studies in mice have shown that hormonal changes in late pregnancy trigger parental instincts and shift priorities.

Pregnancy leads to permanent neural rewiring, according to research that provides new insight into the influence of hormones on behavior.

According to The Guardian, a study on mice found that their parental instincts were triggered by changes in the brain that occur in response to estrogen and progesterone in late pregnancy. According to scientists, similar changes are likely to occur in the human brain.

The researchers said the work could pave the way for new understanding of parenting behavior and postpartum mental health.

Dr Jonny Kohl, who led the study at London’s Francis Crick Institute, said: “We know that women’s bodies change during pregnancy to prepare them for parenting. One example is milk production, which begins long before birth. Our research shows that such preparations also occur in the brain.”

The findings are consistent with brain imaging studies in women showing changes in brain volume and brain activity that persist long after pregnancy. However, Dr. Kohl notes that “raising children is obviously much more complex in humans.”

The studies were conducted on mice whose behavior undergoes dramatic changes: virgin females show no interest in their pups, and mother mice spend most of their time looking after the pups.

Previously, it was widely assumed that the onset of these behaviors occurred during or immediately after birth, perhaps triggered by hormones such as oxytocin. However, recent research extends the changes to an earlier stage and also suggests that the changes may be permanent.

The scientists used miniature devices attached to the heads of mice to record directly from a population of neurons in the hypothalamus that were already associated with parental behavior.

Brain recordings showed that estrogen reduced the baseline activity of these neurons, but made them more excitable in response to incoming signals. Progesterone changed their input signals, causing them to form more synapses so that these neurons were more tightly connected to other parts of the brain—and these changes appeared to be permanent.

“We think these changes, often referred to as the ‘baby brain’, cause a shift in priorities – virgin mice focus on mating so they don’t need to respond to other females’ babies, while mothers need to demonstrate consistent parenting behavior to ensure survival cubs, says Dr. Kohl. “What’s amazing is that this switch doesn’t happen at birth—the brain prepares for these big changes in life much earlier.”

When mice were engineered to have neurons that were insensitive to hormones, they showed no switch to parental behavior even after birth, suggesting that there is a critical window during late pregnancy when these hormones take effect.

In humans, hormonal changes are not the only or even necessarily the main factor influencing parental behavior. But understanding the changes that occur in the brain could provide new insights into the impact on parental bonds and conditions, including postpartum depression and psychosis.

Professor Robert Froemke from New York University Langone, who was not involved in the study, said: “We still don’t understand much about parenting and hormonal signaling in the body and brain – these results are a major step in that direction. Parenting is one of the most complex behaviors that we and other animals engage in, and there is not much room for “trial and error,” especially in the early days after birth when babies require a lot of care.

“The hormonal changes documented here appear to help the parental brain respond to the infant’s needs immediately after birth, so that rodent parents, much like new human parents, can do a good job and be sensitive to their babies as as soon as possible,” added Professor Froemke.