The science behind memory lapses and mental fog during pregnancy

“Why did I walk into this room again?” For many pregnant women, that question becomes an almost daily occurrence.

Forgotten appointments, misplaced keys, unfinished sentences, and walking into a room only to forget the purpose can leave expectant mothers wondering if something is wrong.

The phenomenon is so common that it has earned its own nickname: pregnancy brain, a long-used cliche to describe women becoming forgetful and feeling less capable during pregnancy.

But a recent study, the largest to date, indicates that pregnancy has a profound structural impact on brains and offers new clues into the neurological changes in mums‑to‑be.

In a study by the NeuroMaternal laboratory at the Gregorio Marañón Health Research Institute in Madrid, researchers found that emotions and empathy decrease by an average of nearly 5% during pregnancy.

“It suggests that grey matter, the nerve-rich part of the brain involved in processing information, emotions and empathy, decreases by an average of nearly 5% during pregnancy,” reads the study in part.

According to the study, the brains of 127 pregnant women were scanned – before, during and after pregnancy – and compared to scans from a smaller number of women who were not expecting.

The greater the changes in the brain, the more likely women were to say they were relating to, and bonding well, with their babies – the team of scientists found.

Susan Camora, one of the researchers, explained that Pregnancy changes many organs in the body – the mum’s heart can grow bigger, the capacity of her lungs can increase – and so it makes sense pregnancy can change the brain too.

How pregnancy changes the brain

In another study by Dr Colleen Cagno, who is a family medicine physician with Banner University Medicine, sheds light on the science behind mommy brain, how it affects new parents.

“One interesting study used brain scans (MRIs) to look at changes in the brain before, during and after pregnancy,” Dr. Cagno said. “It showed that the brain’s gray matter (which is important for thinking and decision-making) decreases during pregnancy. At the same time, white matter (which helps different parts of the brain communicate) increases in certain areas.” 

These changes are thought to help the brain focus on new behaviors, like bonding with and caring for a baby. In particular, the brain changes in areas that help with social processing, like understanding emotions and reading other people’s cues.

These changes help parents better respond to their baby’s needs, strengthening their bond.