Every year, 140 million women become pregnant and 134 million give birth to new babies. The phenomenon is so common that its strangeness can be overlooked: how adult human beings, sometimes not even young, emerge with untapped potential. Even though scientists often delve deeper into the mysteries of everyday life than anyone else, the unknowns surrounding pregnancy abound. Gastrulation, the process in which a sphere of a few hundred cells transforms into what will later become an individual, remains an enigma. And, despite the undoubted importance of pregnancy, it is also unknown what happens to all those millions of women who give birth every year. This is beginning to change.
The magazine Nature Neuroscience publishes a work today Monday In this article, a group of scientists from the University of California describe how Elizabeth Chrastil, a researcher from the University of California, Irvine (USA), who also wrote the article, followed the pregnancy of a 38-year-old woman in detail from three weeks before conception until two years after giving birth. Emily Jacobs, a researcher from the University of California, Santa Barbara and co-author of the study, explains that studies on brain changes during pregnancy are usually done by taking measurements of many people at a single time. “This group approach does not tell us how the brain changes day by day,” she says. To overcome this problem, in their work, they performed 26 magnetic resonance imaging (MRI) scans of a single person, to have an accurate image of what happened to her at each stage of pregnancy and also before and after.
Women experience intense hormonal changes throughout their lives, with important consequences for their physical and emotional state, from menstruation to menopause. During the 40 weeks of gestation, the mother’s body adapts to support a new human being. Blood volume can increase by more than a litre, the amount of oxygen and energy consumed increases and the production of hormones such as oestrogen or progesterone increases by up to a thousand times. This explosion has effects on the central nervous system, which reorganises itself.
In animal models, hormones have been shown to drive the production of neurons or grow the dendritic spines through which nerve cells communicate. “In mice, the surge in estrogen and progesterone programs brain circuits, especially in the hypothalamus, and this remodeling increases the mother’s sensitivity to the smells and sounds of her newborn pups.” […] and can trigger maternal behaviors like nest building, licking, and grooming,” Jacobs explains, noting that in humans the story is more complex. In humans, “parental behavior happens all the time in non-gestational mothers, foster parents, grandparents, and fathers who may not experience gestation firsthand but still display all the necessary caregiving behaviors for their offspring,” she says.
In the study published today, they observed a generalized reduction in gray matter and in the volume and thickness of the cerebral cortex from the ninth week of pregnancy, particularly in areas such as the default mode network, associated with processing information necessary for social relationships. Although this may sound like something negative, the authors clarify that it is not. It is actually a process of adaptation to a new circumstance that requires a certain specialization to improve the relationship with the baby. This type of brain reorganization also occurs during adolescence, another transitional period with intense hormonal activity.
Some of the changes observed during pregnancy were reversed two months after birth, but others, such as the reduction in the volume of the cerebral cortex, persisted for at least two years after birth. Although the study only followed up two years after birth, others have found pregnancy-related changes up to six years after giving birth, and there are algorithms and machine learning systems that, decades after childbirth, are able to distinguish the brains of women who have been pregnant from those who have never been pregnant.
Chrastil, co-author and sole subject of the study, says that despite what her brain scans showed, she didn’t feel any different during pregnancy. “Some people talk about things like mom brain“But I didn’t experience any of that,” she says. “There are a lot of things going on, like you’re sleeping less or you’re feeling anxious or stressed, but we don’t necessarily know what to attribute them to. We could attribute it to pregnancy, but we don’t really know,” says the researcher, who says it’s still too early to link changes in behaviour or mental state in pregnant women with the changes seen in her study. Science is not rushing and Chrastil’s son is already four years old, the time needed to gather and process the information from this study.
The American researchers present this article as part of the work of a international consortium The aim of this study is to unravel the mysteries of the pregnant woman’s brain. The Spanish Susana Carmona, from the Gregorio Marañón Hospital in Madrid, a pioneer in this type of study, is also participating in this project. In an opinion collected by the SMC Spain, Carmona points out that “the way forward now is to evaluate this phenomenon in a larger number of subjects in order to see what relationship these changes have with factors that show a high variability between subjects: type of delivery, breastfeeding, symptoms of depression, socioeconomic status, maternity leave…” “Without a doubt, this and other studies focused on characterizing brain changes in pregnant women can help us understand, predict, and prevent postpartum mental pathology, among other phenomena. But we are still far from making specific recommendations,” she concludes. In the work to understand how the brain changes after having children, it will also be interesting to measure the changes associated with parenting, beyond pregnancy, and that It’s not just mothers’ brains that change.
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