Motherhood 'brain boost' unproven

“Having a child makes you more intelligent,” according to the Daily Mail. The newspaper says that this is contrary to the “popular belief” that pregnancy can “dim brain power”.

This story is based on a small study which looked at the brains of 19 new mums, using scans to understand how they changed between two weeks and four months after having a baby. It found that the volume of the certain parts of the brain increased in this period, and that this increase seemed to be greater among women who used more positive words to describe their baby.

Contrary to what is implied by the newspaper, the study did not assess the women’s intelligence, and it is not possible to say whether the changes in brain volume led to any changes in intelligence or behaviour. Also, the study did not examine any women without children, so we cannot say whether the effect only occurs after birth or if it occurs in other situations where new skills must be learnt.

Where did the story come from?

The study was carried out by researchers from Yale University School of Medicine and other research centres in the US and Israel. It was funded by Cornell University, the US-Israel bi-national science foundation, the Institute for the Study of Unlimited Love, the Associates of the Yale Child Study Center, and a number of US governmental health agencies.

The study was published in the peer-reviewed journal Behavioural Neuroscience.

This study was covered by the Daily Mail and The Daily Telegraph. The Daily Mail’s report suggests that the study has looked at intelligence, which it did not. The Telegraph gives a more accurate representation of the research, and importantly notes that “these early findings require replication with a larger and more representative sample”.

What kind of research was this?

This was a case series looking at structural changes in the brains of mothers up to four months after having a baby. The researchers say that studies in animals have suggested that structural changes occur in the brain in the period just after birth, and that these changes are related to changes in maternal behaviour. Therefore, they wanted to see whether there were similar changes in humans.

This type of study is an appropriate way to look at what happens in mothers’ brains after birth. However, this study did not feature a comparison group of women who had not given birth, so it cannot tell us whether any changes observed occur solely after birth or if they are related to other situations involving learning new skills.

What did the research involve?

The researchers enrolled 19 women and scanned their brains two to four weeks after giving birth, and three to four months after birth. They then compared the volumes of grey matter and white matter in the brain at these time points, both as a whole and in specific brain areas. The grey matter of the brain contains the main ‘body’ of the nerve cells. The white matter contains the long projections from the nerve cells (called axons), which connect them with other distant nerve cells or other cell types.

Women who had full-term, healthy babies at one hospital in the US were asked to participate. All of the mothers were white, married or living with a partner, and were breastfeeding. For 11 of the mothers this was their first child.

At the first brain scanning appointment the researchers used a standard questionnaire to interview the women about their experience of being a parent at two to four weeks after birth. This included asking mothers to select words from a list of adjectives that best described their perception of the baby and of their experience as a mother. The list for perception of their baby included 13 positive words such as “beautiful”, “perfect” and “special”, and the list for perception of their feelings as a mother included 32 positive words, such as “blessed”, “content” and “proud”. The researchers then added up the number of positive words selected in each category.

The researchers used a technique called high resolution scanning magnetic resonance imaging (MRI) to assess the women’s brains at two to four weeks after giving birth, and three to four months after birth. The researchers then looked for changes in the brain over this period, and whether they differed in relation to the levels of positive feelings expressed at the start of the study.

What were the basic results?

On average, the women used 6.11 positive words out of 13 to describe their baby, and 8.21 positive words out of 32 to describe their parenting experience two to four weeks after birth.

Between the first and second brain scan, women showed an increase in the grey matter volume in several areas of the brain, including the superior, middle and inferior prefrontal cortex, precentral and postcentral gyrus, superior and inferior parietal lobe, insula and thalamus. No areas of the brain showed a reduction in grey matter volume.

Women who gave a greater number of positive words to describe their baby at two to four weeks after birth showed greater changes in grey matter volume in certain areas of the brain (hypothalamus, amygdala, and substantia nigra). There was no relationship between the number of positive words used to describe their parenting experience at two to four weeks after birth and change in grey matter volume in these areas.

How did the researchers interpret the results?

The researchers conclude that “the first months of motherhood in humans are accompanied by structural changes in brain regions implicated in maternal motivation and behaviours”.

Conclusion

This small study suggests that there are some structural changes in mothers’ brains in the months after birth. However, there are a number of limitations:

• The sample was very small (19 women) and only included a group of women who had similar characteristics (e.g. all white, and all breast feeding). A larger, more varied group would be needed to confirm whether similar changes occur in all women who have given birth.
• As there was no control group of women who had not given birth, it is not possible to say whether these types of brain changes also occur in other circumstances not specifically related to motherhood.
• Although there was a relationship between grey matter changes and the number of positive words used to describe their baby at two to four weeks after birth, it is not possible to say for certain that this difference was related to the brain changes seen. There are many other characteristics and experiences that may have differed between the women and could be responsible for the changes.
• It is not possible to say what effect, if any, the observed changes would have on a woman’s emotions, behaviour or intelligence.

This study will be of interest to scientific research, but there are no practical implications for women who have given birth or for their care.