Scientists have discovered that there may be a reason why "one pregnancy makes a woman stupid for three years"

I believe everyone has heard the saying "pregnancy makes women stupid for three years". During pregnancy, women will experience significant hormone fluctuations and various physiological changes. But will they also become "stupid"? Recently, scientists have conducted research on this and found that the saying "pregnancy makes women stupid for three years" does have scientific basis.

Recently, researchers from the University of California, Santa Barbara, for the first time used technologies such as magnetic resonance imaging (MRI) and functional magnetic resonance imaging (fMRI) to dynamically record changes in women's brain structure throughout pregnancy, providing precise imaging basis for understanding the psychological and physiological changes in women as pregnancy progresses.

The research results were published in Nature Neuroscience on September 16, 2024.

Human gestation lasts about 40 weeks. During this period, the mother undergoes profound physiological adaptations to support the development of the fetus, including significant increases in plasma volume, metabolic rate, oxygen consumption, and immune regulation. These changes are caused by a hundreds- to thousands-fold increase in the secretion of hormones such as estrogen and progesterone. The increase in hormone levels during pregnancy not only affects the body, but also brings profound changes to the brain.

Typical changes in estrogen (17β-estradiol) and progesterone levels: a significant increase throughout pregnancy and a sharp decline after delivery[1]

In this latest study from the University of California, the subject was a healthy 38-year-old woman who was pregnant for the first time. She underwent 26 MRI scans and blood tests from the time she was preparing for pregnancy to 2 years after giving birth. The study found that the entire process of pregnancy had an impact on multiple key areas of the brain, and these changes were significantly associated with increased hormone levels.

Magnetic resonance imaging showed that as pregnancy progressed and estrogen and progesterone levels continued to increase, the overall brain volume, cortical thickness, and gray matter volume gradually decreased.

Gray matter is the main component of the cortex, which is rich in neurons, which explains the thinning of the cortex. However, gray matter is also widely distributed in areas outside the cortex, such as the ventral diencephalon that regulates emotions and the hippocampus related to memory and learning, where the volume of gray matter has decreased.

The study also noted that changes in gray matter volume were associated with specific brain networks.

For example, in the network area that responds to emergencies, the gray matter volume decreased by about 8%, and in the network that helps focus attention and perform complex analysis, the gray matter volume decreased by about 6%. But on the contrary, in the network area that processes emotional memories and establishes emotional connections between mothers and babies, the gray matter volume increased by about 2%. The volume of gray matter will begin to recover after delivery, but it is relatively slow. This study tracked the thickness of the cerebral cortex and the overall changes in gray matter until the second year after delivery, and the thickness of the cerebral cortex and the overall changes in gray matter have not returned to baseline levels. In fact, in January of this year, a team from the Carlos III Health Institute in Spain also published data on the thinning of the cerebral cortex thickness in women in late pregnancy and after delivery, and pointed out that this change may continue for several years, but the data at the time did not include early pregnancy.

Based on this research, the saying "pregnancy will make women stupid for three years" may have some basis for its truth.

"Pregnancy stupidity" may be the result of the brain reallocating energy and attention in order to adapt to the new role of mother. The purpose is to reduce overreaction to external stimuli and the burden of complex thinking, so that mothers can focus more on communicating and caring for their babies.

On the other hand, the study also found that the structural integrity of white matter in the brain increased before 27 weeks of gestation.

White matter is a type of nerve fiber tissue widely distributed below the cerebral cortex, responsible for the connection and signal transmission of various parts of the brain. The enhancement of white matter structure helps to better coordinate the functions of different areas of the brain and helps the mother adapt to the physiological and psychological changes brought about by pregnancy and childbirth. However, unlike gray matter, changes in white matter quickly return to normal levels after delivery.

It should be pointed out that this study only observed one woman, and many phenomena cannot be completely concluded. A larger sample size is needed in the future to verify the universality of these phenomena.

But it is the first time that it provides a complete map of brain changes during pregnancy and postpartum, capturing the changes and recovery characteristics of different brain structures, and providing an important basis for further research on the impact of pregnancy on maternal health.

We also hope that with the addition of more samples in the future, related research will bring new ideas to maternal health management, as well as the diagnosis and treatment of pregnancy-related diseases such as postpartum depression and headache.

References:

1. Pritschet, L., Taylor, CM, Cossio, D., Faskowitz, J., Santander, T., Handwerker, DA, ... & Jacobs, EG (2024). Neuroanatomical changes observed over the course of a human pregnancy. Nature Neuroscience, 1-8.

2. Paternina-Die, M., Martínez-García, M., Martín de Blas, D., Noguero, I., Servin-Barthet, C., Pretus, C., ... & Carmona, S. (2024). Women's neuroplasticity during gestation, childbirth and postpartum. Nature Neuroscience, 27(2), 319-327.