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Cognitive Impairment During Pregnancy: Myth or Reality?

Pregnant women experience grey matter volume reductions in brain regions closely tied to the processing of social information, 
such as decoding infant facial expressions and promoting healthy bonding between mother and baby. Credit: CareyHope/iStockphoto

Pregnant women experience grey matter volume reductions in brain regions closely tied to the processing of social information, such as decoding infant facial expressions and promoting healthy bonding between mother and baby. Credit: CareyHope/iStockphoto

By Sasha Davies

While reports of cognitive decline throughout pregnancy are widespread, evidence has been inconclusive. Until now.

“Baby brain” refers to the cognitive decline reported by as many as four out of five pregnant women. Having long been recognised in midwifery folklore, symptoms often include poorer concentration, increased absentmindedness, and feelings of mental “fogginess”, with memory problems being the most frequently reported cognitive complaint during pregnancy.

The impact of these cognitive changes can range from minor day-to-day annoyances to severe disruptions to their personal and professional lives. In personal accounts of this phenomenon, pregnant women have described a variety of consequences including forgetting words mid-sentence, frequently forgetting appointments and, in one severe case, being unable to return to work due to serious memory problems.

However, scientific results from standardised objective tasks testing specific aspects of cognitive performance affected by pregnancy have given only inconsistent results. For example, one small early review of seven published studies from 1969–93 found a significant impairment in pregnant women’s cognitive performance in only half of the tasks tested, with memory being the most affected. However, the authors noted that the results were equivocal across the included studies, and that these studies sometimes did not all use non-pregnant women for comparison.

More recently, an Australian review and meta-analysis of 14 studies compared pregnant and post-birth new mothers to non-pregnant women on laboratory measures of memory (https://goo.gl/pobS63). While the results indicated that pregnant women’s memory performance was worse on some memory tasks, this was not the case for all memory tasks. Instead, it seems that only those tasks that place a high cognitive demand on the pregnant women were affected.

Taken together, these inconsistencies have meant that a question has still remained about whether women should expect cognitive changes during pregnancy.

Dispelling the Myth

Given the varied landscape of the current literature, my team and I sought to clarify whether new data published over recent years could finally dispel the confusion surrounding potential cognitive changes during pregnancy. Our new study, published in the Medical Journal of Australia (https://goo.gl/xUwt13), has confirmed that pregnancy does indeed appear to impact on women’s cognitive functioning, particularly in memory, attention and executive functioning.

We combined data from 20 studies reporting the relationship between pregnancy and cognitive functioning, and pooled these differences together to assess the cognitive performance of 709 pregnant women and 521 non-pregnant women.

Our results showed that when pregnant women are compared with non-pregnant women, their performance on tasks measuring memory and executive functioning – a broad term referring to high cognitive processes like attention, decision-making, planning, judgement and inhibition – is much worse. Moreover, this difference was most obvious at the third trimester of pregnancy.

Women were tested with tasks such as the digit span test, which asks participants to listen to a set of numbers read aloud and then repeat them in either forward or reverse order. We found that when the same women were tested at several points during their pregnancies, the decline appeared to start during the first trimester before stabilising from the middle to the end of the pregnancy.

While these results are interesting, it is important to note that the pregnant women were still broadly performing in the normal range of functioning. This suggests that while some pregnant women may notice that they don’t feel as sharp as they did before pregnancy, these changes are not likely to have a dramatic impact on their ability to perform at normal levels in their personal and professional lives.

Indeed, given the massive number of physiological, emotional and social changes occurring during pregnancy, these results are a clear testament to the resilience and adaptability of women during pregnancy.

What Causes Cognitive Impairment During Pregnancy?

Our study is the first to explore how pregnancy may affect other cognitive areas beyond memory and to specifically look at when pregnant women are most likely to experience the effects of baby brain. However, there is still a lot of speculation about what might cause these changes, and research in this field has a long way to go before any definitive answers can be established.

Nevertheless, recent intriguing research into brain structure changes have shown that pregnancy affects grey matter volume both during and after pregnancy. The study, published in Nature Neuroscience (https://goo.gl/1ni4vv), used MRI to scan the brains of 25 women before and after pregnancy. The results showed that the pregnant women experienced grey matter volume reductions in brain regions closely tied to the processing of social information, such as decoding infant facial expressions and promoting healthy bonding between mother and baby. Interestingly, no such effects were observed in male spouses scanned at matched time points.

However, these reductions do not mean that pregnant women are simply “losing function”. Indeed, adolescents also experience similar grey matter volume reductions, and this has been viewed as part of the natural neural pruning process of brain maturation and specialisation. In terms of brain volume and structure, it therefore seems that bigger is not always better.

Other studies have also supported this by finding that pregnant women are better at recognising novel faces (i.e. faces of strangers) compared with non-pregnant women, and were also more adept at recognising threats in the environment. Together, this presents a compelling idea that the cognitive changes experienced during pregnancy are an important adaptive fine-tuning that helps women prepare to raise their children by allowing their brains to adapt to their new role as mothers.

Future Research Is Still Needed

There are still several questions that need to be answered to improve our understanding of this fascinating relationship between pregnancy and women’s cognitive functioning. First, much of the available literature focused only on measuring cognitive changes without examining whether these differences were still evident in the postpartum period. This means that it is still unclear whether the memory and executive functioning changes in our study extend into the early stages of parenthood and, if so, how long these effects might last.

Second, there is still the unanswered question about the underlying causes of these cognitive differences during pregnancy. It is well-established that pregnancy is a time of monumental physiological, psychological and social changes, including hormonal shifts (e.g. oestrogen, progesterone and oxytocin), mood changes, sleep disruption, increased stress, dietary changes, nausea and preoccupied thinking patterns, all of which are normal experiences of pregnancy. Each of these factors impacts on cognitive functioning in other participant groups, including healthy, non-pregnant adult women and men. This suggests that pregnancy-related cognitive change could be attributed to any one of these underlying factors, or perhaps an interaction of all of them.

In an effort to answer some of these questions, we are continuing this research by conducting a study tracking women during the pre-conception phase, throughout pregnancy and up to 12 months post-partum. We are currently recruiting for women in the Melbourne region who are either actively trying to become pregnant or who are currently pregnant in their first trimester. We would also be delighted to hear from any interested academics and members of the public for future collaborations in this area.


Sasha Davies is a PhD candidate at the Cognitive Neuroscience Unit in Deakin University’s School of Psychology.