Pregnancy can bring many changes to the body but some women also notice something less visible: difficulty remembering names, losing track of conversations or walking into a room and forgetting why they went there.
Often called “momnesia,” “baby brain” or “pregnancy brain,” the phenomenon has long been reported by pregnant women. New research now offers a possible biological explanation, pointing to the way rising estrogen levels may temporarily alter communication between brain regions involved in hormone regulation and memory.
The study, published in Science Bulletin, combined experiments in mice with memory testing in pregnant women. Researchers found evidence suggesting that sustained high estrogen levels may influence a neural pathway connecting the hypothalamus and hippocampus.
How Hormones May Affect Memory
Estrogen is essential to pregnancy. Levels of the hormone rise substantially as pregnancy progresses and reach their highest levels during the third trimester.
Researchers led by scientists including Dr Zheng Sun of Baylor College of Medicine examined what happens when the brain is exposed to similarly elevated estrogen levels.
Their experiments focused on the hypothalamus, a region involved in regulating several important bodily functions and the hippocampus, which plays a central role in learning and memory.
The researchers found that elevated estrogen increased the activity of particular neurons in the hypothalamus. This appeared to suppress activity in the hippocampus, producing temporary memory problems in mice.
The findings suggest that the effect is not simply a broad decline in brain function.
What the Mouse Experiments Showed
The researchers gave laboratory mice sustained exposure to high estrogen levels and then tested their ability to recognise objects and remember locations.
The mice exposed to higher estrogen showed poorer performance on several memory tasks than comparison animals.
Researchers then manipulated the neural connection between the hypothalamus and hippocampus.
When the pathway was switched off experimentally, the estrogen-related memory problems disappeared. Activating the pathway, meanwhile, produced memory difficulties even without elevated estrogen.
The team also examined the role of estrogen receptor alpha, a protein that allows cells to respond to estrogen. Removing these receptors from the relevant hypothalamic neurons prevented the memory effects in the experiments.
The results provide evidence for a specific biological mechanism rather than simply showing that pregnancy is associated with forgetfulness.
Evidence From Pregnant Women
The researchers also studied 70 women, including pregnant participants at different stages of pregnancy and women who were not pregnant.
Participants completed tests assessing different forms of memory, including short-term, long-term and working memory.
Memory difficulties were most apparent during late pregnancy, when circulating estrogen levels were also higher.
The researchers reported an association between higher estrogen concentrations and poorer performance on several memory-related tests, even after accounting for other possible factors.
That human evidence supports the mechanism suggested by the animal experiments but researchers stressed an important limitation.
They did not directly measure or manipulate the hypothalamus-to-hippocampus pathway in pregnant women. As a result, the human findings cannot establish the same cause-and-effect relationship demonstrated in the mouse experiments.
Not a Sign of Lower Intelligence
Scientists involved in the research stressed that pregnancy-related forgetfulness should not be interpreted as a general reduction in intelligence or cognitive ability.
Instead, the changes appear to affect particular types of memory and may be relatively subtle.
Women may notice practical effects such as forgetting appointments, misplacing objects, struggling to recall familiar words or losing the thread of a conversation.
Dr Sun said such changes are common but generally not medically disabling. They can nevertheless affect everyday functioning and a person’s confidence.
A Temporary Change
Pregnancy-related cognitive changes are generally most noticeable in the later stages of pregnancy and can continue for a period after childbirth.
For many women, memory function returns toward normal as the body adjusts to the major hormonal changes associated with pregnancy and the postpartum period.
The new study adds to growing evidence that pregnancy is accompanied by significant changes in the brain as well as the rest of the body.
Rather than treating “momnesia” simply as a joke or everyday inconvenience, researchers are beginning to investigate the biological processes behind it. The latest findings suggest that changing hormones may temporarily reshape how different parts of the brain communicate, offering a clearer explanation for a familiar experience of pregnancy.
Jaweria Nazeer
About Author:
The author is a writer who focuses on social issues and nutrition. Their work highlights topics such as inequality, education, human rights and healthy lifestyle habits aiming to inform readers and promote positive awareness and change.
Keywords: momnesia, momnesia pregnancy, pregnancy brain, baby brain, pregnancy forgetfulness, pregnancy memory loss, estrogen and memory, pregnancy hormones, brain changes during pregnancy, maternal health
Asian Burg / Health | Science
