A woman’s brain changes in very different ways during her second pregnancy than during her first, helping her adjust to the demands of parenting a large family.This discovery has come to light from a study published in the journal Nature Communications by researchers at the Amsterdam University Medical Center. Scientists already knew that first pregnancy causes structural changes in the brain. This new study shows that subsequent pregnancies don’t simply repeat those changes. Instead, each pregnancy leaves its own unique imprint on the mother’s brain.The team followed 110 women, having their brains scanned before pregnancy and again after childbirth. Some of the women were pregnant for the first time, some were expecting their second child, and a control group remained childless. By comparing the groups, researchers identified the exact physiological changes that occur when a woman becomes a mother for the second time.
shifting attention from inside out
During the first pregnancy, the greatest changes occur in the brain’s default mode network. This network is responsible for self-reflection, daydreaming, and understanding social situations.During the second pregnancy, this network changes again, but much less than the first time. Instead, the biggest changes occur in areas of the brain that control attention and process physical sensations, helping moms focus more on the outside world.“It appears that during the second pregnancy, the brain changes more strongly in the networks involved in responding to sensory signals and controlling your attention,” said researcher Milou Strathof, who analyzed the study data. “These processes can be beneficial when caring for more than one child.”Physical changes included reductions in gray matter volume, surface area, and cortical thickness in some parts of the brain. The average reduction in cases of second-time mothers in these areas was 2.8 percent. First-time mothers had a slightly larger decrease in brain area of 3.1 percent, which was 79 percent larger than second-time mothers.Using advanced computer analysis, researchers looked only at these brain changes and were able to correctly identify whether a woman had completed her first or second pregnancy with 80 percent accuracy.The scans also revealed that although the brain began to recover in the months after birth, it never returned to its original state before pregnancy in either group. The length of time since a woman’s first birth also does not affect the brain changes seen during her second pregnancy.
Bonding and keeping an eye on depression
The researchers also compared these brain changes to the mothers’ emotional experiences. They found a clear connection between physical changes in the brain and how strongly a mother attached to her baby.This association was stronger after the first pregnancy than the second. For first-time mothers, the changes in the brain closely match their initial feelings of attachment to both the unborn baby and the newborn. For women becoming mothers for the second time, the same relationship was still present but involved fewer brain areas.The study also provides the first direct evidence that changes in the outer layers of the brain are linked to peripartum depression. However, the timing of this risk depends on whether this is the woman’s first or second pregnancy.For first-time mothers, the strongest association between brain changes and depressive symptoms appeared after childbirth. For women having a second child, this association appeared much earlier, while they were still pregnant. In both groups, women who showed fewer brain changes reported higher levels of depression and emotional distress.“With this, we have shown for the first time that the brain not only changes during the first pregnancy, but also during the second pregnancy,” said Elselin Hoekzema, head of the Pregnancy Brain Lab at Amsterdam UMC. “During the first and second pregnancies, the brain changes in both similar and unique ways. Each pregnancy leaves a unique imprint on the woman’s brain.”
long term health implications
For many years, scientists have known little about how multiple pregnancies affect the human body throughout life. Earlier studies on animals have shown that rodents experience permanent changes in brain structure and hormone activity depending on how many babies they have, but similar evidence in humans is limited.By showing that the human brain continues to reshape itself during subsequent pregnancies, the Amsterdam UMC study fills an important gap in women’s health research. Researchers say the findings highlight the brain’s ability to adapt during major life changes.“This knowledge may help to better understand and identify mental health problems in mothers,” Hoeksema said. “It is important that we understand how the brain adapts to motherhood.”The team hopes these findings will help doctors better predict, identify and treat mental health problems in mothers. Knowing that second-time mothers experience significant brain changes early in pregnancy could change the way doctors screen for anxiety and depression before birth.The findings may also help explain why previous international studies have linked multiple pregnancies to younger biological brain age and different risks of neurological diseases in later life. Because the brain’s attention and sensory networks become more active during the second pregnancy, these changes may help protect the brain as women age.