A second pregnancy changes the brain in surprising new ways
A woman’s brain changes in very different ways during her second pregnancy compared to her first, helping her adapt to the demands of raising a larger family.This discovery comes from a study conducted by researchers at the University of Amsterdam Medical Center, and published in the journal Nature Communications.
Scientists already knew that the first pregnancy causes structural changes in the brain.
This new study shows that subsequent pregnancies do not simply repeat these changes. Instead, each pregnancy leaves its unique mark on the mother’s brain.The team followed 110 women, giving them brain scans before pregnancy and again after giving birth. Some of the women were pregnant for the first time, some were expecting their second child, and the control group remained childless.
By comparing the groups, the researchers identified the subtle physical changes that occur when a woman becomes a mother for the second time.
Shift the focus from the inside out
During the first pregnancy, the biggest 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 the areas of the brain that control attention and process physical sensations, helping mothers 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 Milo Strathoff, the researcher who analyzed the study data. “These processes may be useful when caring for multiple children.”Physical changes included a decrease in gray matter volume, surface area, and cortical thickness in certain parts of the brain. In second-time mothers, the average decrease in these areas was 2.8 percent. First-time mothers saw a slightly greater reduction of 3.1% in the area of the brain that was 79% greater than that affected in second-time mothers.Using advanced computer analysis, the researchers looked only at these brain changes and were able to determine with 80% accuracy whether a woman had completed her first or second pregnancy.The scans also showed that although the brain began to recover during the final months after birth, it never returned to its original pre-pregnancy state in either group. The amount of time that had passed since a woman’s first birth also did not affect the brain changes seen during her second pregnancy.
Tracking interdependence and depression
The researchers also compared these brain changes with mothers’ emotional experiences. They found a clear link between physical changes in the brain and how strong a mother’s attachment to her child is.This association was much stronger after the first pregnancy than after the second. For first-time mothers, brain changes correspond closely with their early feelings of attachment to both the unborn child and the newborn. For second-time mothers, the same connection was still there but involved fewer areas of the brain.The study also provides the first direct evidence that changes in the outer layer of the brain are linked to perinatal 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 link emerged between brain changes and postpartum depression symptoms. For women who had a second child, the connection appeared much earlier, while they were still pregnant. In both groups, women whose brains showed fewer changes reported higher levels of depression and emotional distress.“With this, we have shown for the first time that the brain changes not only during the first pregnancy, but also during the second pregnancy,” said Elseline Hoekzema, head of the Pregnancy Brain Laboratory at the Medical University of Amsterdam. “During the first and second pregnancies, the brain changes in similar and unique ways. Each pregnancy leaves a unique mark on the female brain.”
Long-term health effects
For many years, scientists knew very little about how repeated pregnancy affects the human body over the course of a lifetime.
Previous animal studies have shown that rodents experience permanent changes in brain structure and hormonal activity depending on the number of litters they have, but similar evidence in humans has been limited.By showing that the human brain continues to remodel itself during subsequent pregnancies, the Amsterdam Medical University 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 can help better understand and identify mental health problems in mothers,” Hoekzema said. “It is important to 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 important brain changes early in pregnancy could change how doctors screen for prenatal anxiety and depression.The findings may also help explain why previous international studies have linked multiple pregnancies to younger biological brain age and different risks of developing neurological diseases later in life. Because the brain’s attention and sensory networks become more active during the second pregnancy, these changes may help protect the brain as the woman gets older.
