Wednesday April 8 2015
Baby brain – real or just a stereotype?
"'Baby brain' is a stereotype and all in the mind,
the Mail Online reports.
The headline is prompted by a US study that aimed to see if "baby brain" (aka "mumnesia") – alleged memory lapses and problems with concentration during pregnancy – is a real phenomenon or just a myth.
The study recruited 21 women in the third trimester of pregnancy. A second group of 21 women who had never been pregnant were recruited to act as a control. The women completed a variety of tests to measure their memory, attention and problem solving ability. The tests were repeated several months later and the two groups compared.
Though the pregnant women reported greater memory difficulties, there were no differences in the results of the tests between the two groups.
The researchers say this shows that pregnancy and childbirth do not affect the ability to "think straight". However, we do not know what the level of performance would have been for the pregnant women before they were pregnant. It is also possible that the small numbers of women in each group could have affected the results. The findings could be completely different with a different sample of women.
This study does not provide conclusive evidence that pregnancy has no effect on memory and attention.
Seeing that pregnancy can often cause tiredness, it would be surprising if some women didn’t have temporary problems with memory and concentration.
Where did the story come from?
The study was carried out by researchers from Brigham Young University in Utah. It was funded by the Brigham Young University College of Family, Home and Social Sciences, and the Women’s Research Institute at Brigham Young University.
The study was published in the peer-reviewed Journal of Clinical and Experimental Neuropsychology.
The Mail Online reported the story reasonably accurately, but did not explain the major limitation of the study's design – that it does not take into account the memory and problem solving abilities of the women before they became pregnant.
What kind of research was this?
This was a case-controlled study that aimed to see if cognitive ability (memory and problem solving) changed in pregnancy and after childbirth. Previous research has found mixed results, with some studies indicating improved cognitive abilities during pregnancy and some showing a reduction or no difference.
This type of study can show associations, but cannot prove that any cognitive differences are due to the pregnancy, as other factors could cause the results.
What did the research involve?
The researchers recruited 21 pregnant women and a control group of 21 healthy women who had never been pregnant. The women completed a variety of tests to measure their cognitive ability. The tests were repeated several months later and the two groups compared.
The women were given 10 neuropsychological tests, which measured their memory, attention, language, executive abilities (such as problem solving) and visuospatial skills (the ability to process and interpret visual information about where objects are). They also filled out questionnaires to assess their mood, and levels of anxiety, quality of life, enjoyment and satisfaction.
Each test was conducted when the pregnant women were in their third trimester and repeated between three and six months after giving birth. The non-pregnant women were also tested twice, with a similar time gap between the tests.
Women were excluded from the study if they had a history of:
- learning disabilities
- attention deficit hyperactivity disorder (ADHD)
- psychotic or bipolar disorder
- traumatic brain injury
- substance abuse/dependence
The results were then analysed during and after pregnancy, and compared to the controls. Further analysis was performed in the pregnancy group, comparing women in their first pregnancy with women who had previously given birth.
What were the basic results?
The pregnant women were older, on average, with a mean age of 25, compared to 22 for the control group. 11 of the pregnant women and nine of the controls were students.
The main results were:
- No difference between the groups in terms of language ability or memory, though the pregnant women reported worse memory than controls.
- No difference between tests of attention and visuospatial ability, with higher scores for both groups in the second session of tests.
- Executive functioning also improved for both groups. For one of the tests, the Trail Making Test, the pregnant women were slower at Part A both during and after pregnancy. Part A measures visual scanning and processing speed by asking the participant to draw a line as quickly as possible between consecutive numbers randomly written on paper. Part B measures scanning and processing speed, but also mental flexibility by requiring the person to join each consecutive number and letter: 1-A-2-B-3-C etc. There was no difference in scores for Part B between the groups.
Pregnant women reported a lower quality of life and were more likely to have depressive symptoms compared to controls. The results were as follows:
- Six pregnant women had mild symptoms of depression during pregnancy. One of them continued to have mild symptoms after birth. These women performed similarly to the control women in the neuropsychological tests.
- One woman had moderate symptoms of depression during pregnancy and developed severe symptoms by the second test after birth.
- No women in the control group had significant symptoms of depression.
There were no differences between women in their first pregnancy compared to women who had previously given birth.
How did the researchers interpret the results?
The researchers say their "findings suggest no specific cognitive differences between pregnant/postpartum women and never-pregnant controls". This was despite the pregnant/postpartum women reporting more memory difficulties.
The researchers conclude that although the pregnant women reported memory problems, these did not show up on their tests. However, this does not take into account their pre-pregnancy ability. The women may have performed better before they got pregnant, which is why they are now reporting memory problems. None of these women were tested before they got pregnant, which is the major limitation of the study.
The researchers say that because there were a similar number of students in each group, the women in the control group was a good enough representation of how the pregnant women would have performed pre-pregnancy. However, there will be a wide variation between cognitive abilities, even between different students. There is no information about cognitive abilities, other than the length of time each group were in education. This was an average of 16 years for the pregnancy group, compared to 15 for the control group. The range was the same for each group, at 13 to 18 years.
The other limitation of the study is the small number of women in each group, which limits the strength of the results and makes it more likely that they could occur by chance. A different or larger sample of women could give completely different results.
It is unclear why the pregnant women were slower at the Trail Making Test Part A compared to the controls, but not with Part B. It is likely that the small sample size contributed to this anomaly.
The study highlights the importance of recognising low mood and symptoms of depression in pregnant women and in the months after giving birth. Read more about low mood and depression during pregnancy, and low mood and depression after pregnancy.
In conclusion, this study does not provide conclusive evidence that pregnancy has no effect on memory and attention.
Pregnancy can cause tiredness and fatigue, particularly during the first trimester, and looking after a newborn baby can be exhausting work. Therefore, you shouldn’t feel surprised if you do have the occasional memory lapse or loss of concentration. Dads may not be immune to "baby brain" after the baby is born, either.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.