Dr Glynn also says that just the slightest movement of the foetus in the womb can affect a woman's brain and make her become more sensitive. She claims that even though the woman may not be aware of these movements they will raise her heart rate.
"Pregnancy is a critical period for central nervous system development in mothers, yet we know virtually nothing about it," said Dr Glynn, whose research is published in the journal Current Directions In Psychological Science.
She also says that cells from the foetus will pass into the mother's bloodstream which will also affect the way her brain works.
"It's exciting to think about whether those cells are attracted to certain regions in the brain," she added.
There has been considerable debate in recent years among academics as to whether 'baby brain' really exists. Last year Australian scientists who studied 1200 women claimed there was no evidence to suggest that they had become any more forgetful.
The researchers made women sit memory tests before, during and after pregnancy and found there was very little difference in the scores.
In fact the study claimed that women 'tricked themselves' into thinking they were becoming more absent-minded simply because they had been told this was a likely symptom of pregnancy.
But Dr Glynn insists that we do not know enough about what really happens as there has so far there has been very little research into what actually happens to women's brains during pregnancy.
- DAILY MAIL