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Pregnancy is not just a physical change, it also includes profound changes in the structure and function of the brain. These changes are important for the bond between mother and baby, and also have an impact on the mother's long-term cognitive function. In recent years, neuroscientists have begun to delve into this area to reveal the effects of pregnancy and parenting on the brain. (July 31, Nature "How pregnancy transforms the brain to prepare it for parenthood")
In 2008, neuroscientist Susana Carmona realized in a discussion with her colleagues that research on the effects of pregnancy on the human brain was almost blank. They persuaded their mentor, Oscar Vilarroya, to start a study to measure neuroanatomical changes in women before and after pregnancy using magnetic resonance imaging (MRI) technology. The study lasted eight years and involved dozens of participants, with the final results published in 2016. The study found that several areas of the cerebral cortex shrank by an average of 2% within two to three months postpartum. Although this narrowing may trigger associations of functional loss, studies have found that these changes are positively correlated with the strength of the mother's attachment to the baby. Further studies by Elseline Hoekzema and Susana Carmona showed that areas of the cortex that shrank during pregnancy function differently for at least one year postpartum. These studies reveal that pregnancy, as an important turning point in life, has long been overlooked by the scientific community, even though about 140 million women go through this process each year.
Changes in brain structure During pregnancy, there are changes in the volume of several areas of the brain, including the ventral striatum and hypothalamus, which are associated with reward processing and instinctive behavior control, respectively. The hippocampus, a structure essential for memory, also temporarily shrinks during pregnancy. But it's the cerebral cortex that has the greatest impact, especially those areas that integrate information from other brain regions. A 2016 study showed that brain changes in the immediate postpartum period primarily affect a circuit called the default mode network. This network is associated with social processes such as theory of mind and empathy. The latest research further confirms that the entire cortex shrinks by almost 5% during pregnancy. Most of the postpartum changes are rapidly and completely reversed, but the recovery of the default mode network is different and may not reach pre-pregnancy levels. These changes may be hormone-driven. Hoekzema and Carmona observed that the magnitude of neuroanatomical changes correlated with the levels of estrogen and related hormones, respectively. The data showed that the degree of change in the default mode network was positively correlated with the intensity of mother-infant attachment, response to infant pictures, and nesting behaviours.
Behavioral and cognitive effects on memory deficits during pregnancy are particularly pronounced in the third trimester, which may be related to a decrease in hippocampal volume. However, the impact of these deficiencies on daily life is usually not significant. Data on postpartum cognitive changes were inconsistent, with some studies showing cognitive deficits, some finding no differences, and some even showing increased cognitive function. For example, executive function may be improved in new mothers, an advanced process that is very important in self-regulation and managing competing cognitive needs.
Mental health problemsPregnancy and early parenting are also accompanied by high rates of mental health problems. Globally, postpartum depression affects 17% of new mothers, with the highest incidence in low- and middle-income countries. Psychosis and obsessive–compulsive disorder also have a higher incidence at this stage, although their absolute prevalence is very low. Studies have shown that many of the physiological changes associated with pregnancy, such as shrinking hippocampus, neurochemical and immune changes, resemble those found in depression. Carmona believes that delving into all aspects of pregnancy and beyond, including brain imaging, hormone level monitoring, and psychosocial data, could reveal the mechanisms underlying these changes and ultimately apply them to clinical practice.
Long-term effects and social policy research has also found that the long-term effects of fertility on the brain may help keep the brain young. In 2019, researcher Ann-Marie de Lange used data from the United Kingdom Biobank and found that the brains of women with children looked about seven months younger than those without children. This result suggests that brain plasticity during pregnancy may have a positive effect on the brain. These studies underscore an important message: fertility history should be a routine consideration in biomedical research, as fertility has a profound impact on the brain. The researchers also called for social policies that would take into account the neuroplasticity of this period, such as extended paid maternity leave. Overall, research in this emerging area suggests that pregnancy and parenting not only have a profound impact on the mother's psyche and brain, but may also have important implications for social policy and medical practice. In the future, as more research is conducted, we can hopefully gain a deeper understanding of this complex process.
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