Does Pregnancy Make You Dumber? What the Research on "Baby Brain" Shows

Pregnancy does not make you dumber in the sense of lowering your IQ: the one study that gave women full IQ tests through pregnancy found no decline, and the largest study to test women before they became pregnant found no lasting change. What pregnancy does seem to bring is a modest dip on memory and attention tasks, largest in the third trimester, alongside real changes in brain structure that look more like adaptation than damage.

"Baby brain" or "mommy brain," the forgetful, foggy feeling many women describe, is one of the most common complaints of pregnancy. This page covers what cognitive testing during pregnancy shows, the IQ and prospective studies that put the effect in proportion, what brain scans reveal, why the subjective experience is so much stronger than the test results, and what having children is linked to later in life. It is about the mother's own thinking; the question of how a mother's age relates to her child's intelligence is covered in our article on IQ and maternal age.

Most studies compare pregnant women with women who are not pregnant on short memory, attention and "executive function" tasks, the mental skills used to plan, switch between tasks and hold information in mind. Two meta-analyses summarize them.

• The 2018 meta-analysis: Davies and colleagues pooled 20 studies with 709 pregnant and 521 non-pregnant women. Overall cognitive functioning was poorer in pregnant women, with a "standardized mean difference" (a gap expressed in standard deviations) of 0.52. That is about half a standard deviation, a moderate effect, though the 95% confidence interval ran from 0.07 to 0.97, so the true size is uncertain. The gap appeared mainly in the third trimester, where cross-sectional studies found large but very imprecise differences in general functioning and memory (1.28 and 1.47). Those studies found no significant differences in the first two trimesters, and longitudinal studies, which follow the same women over time, found declines between the first and second trimester (0.29 for general functioning and 0.33 for memory).

• The 2007 meta-analysis: Henry and Rendell pooled 14 studies of memory and found that pregnant women were impaired on some measures and not others. The tasks most affected were those that place relatively high demands on executive control, and the same pattern appeared after birth.

A word on scale. If a gap of 0.52 standard deviations appeared on an IQ test, it would be about 8 points, but none of these studies measured IQ. They used brief memory and attention tasks, which are more sensitive to tiredness and distraction than a full intelligence test, and the effect is an average across many women, with plenty showing no change at all.

Two studies change the picture considerably.

• Full IQ tests across pregnancy: Rutherford and Anderson tested 25 first-time pregnant women and 25 childless women of the same age and education every 12 weeks, alternating between the Wechsler Adult Intelligence Scale and the Stanford-Binet to limit practice effects. Both groups' scores rose with repeated testing. The pregnant women's average full-scale IQ went from 103.4 in the first trimester to 107.7 in the third, slightly more than the rise in the control group (101.8 to 105.2), and after birth the two groups did not differ (106.5 against 108.5). The sample is small, but this is the only study I found that measured IQ itself, and it found no decline.

• Testing women before pregnancy: A central weakness of most "baby brain" research is that women are first tested when already pregnant. Christensen, Leach and Mackinnon avoided this by using the PATH Through Life Project in Australia, which recruited women aged 20 to 24 at random from the electoral roll in 1999 and retested them in 2003 and 2007 on processing speed, working memory and word recall. Seventy-six women were pregnant at a follow-up, 188 became mothers between waves and 542 remained childless. Changes in scores did not differ by pregnancy or motherhood, although late pregnancy was linked to a drop on one of the four tests. The authors suggested that earlier positive findings may reflect biased samples.

Taken together, the better-designed studies point to a small, temporary, task-specific effect that is concentrated late in pregnancy and does not register on a full IQ test.

Brain imaging shows that pregnancy does change the brain, and these findings are the source of many alarming headlines.

• Gray matter reductions: Hoekzema and colleagues scanned first-time mothers before and after pregnancy, along with first-time fathers and childless men and women. Only the mothers showed consistent reductions in gray matter volume, mainly in regions involved in "social cognition," the ability to understand what others are thinking and feeling. The changes were consistent enough to tell apart every woman who had been pregnant from those who had not, they overlapped with regions that responded to the women's own babies after birth, and they predicted measures of the mother's attachment. A follow-up showed the reductions lasted at least two years.

• Week by week: Pritschet and colleagues scanned one healthy 38-year-old first-time mother 26 times, from three weeks before conception to two years after birth. Gray matter volume and cortical thickness fell as pregnancy advanced, in about 80% of the 400 brain regions studied, while measures of white matter integrity rose. Some changes partly reversed after birth. The study did not test cognition, and as the authors note, one person cannot represent all pregnancies.

Less gray matter sounds bad, yet in development it often reflects refinement. Pritschet's team points out that gray matter volume also falls during adolescence, a change tied to gains in executive function and social cognition, and the Hoekzema team interpreted the pregnancy changes as an adaptation serving the transition to motherhood. Brain volume is only modestly related to IQ in the first place: a meta-analysis of more than 8,000 people by Pietschnig and colleagues put the correlation at about .24. These scans cannot be read as a loss of intelligence.

Orchard and colleagues, in a 2023 review, report that about 80% of new mothers describe cognitive decline. That figure is far larger than anything the tests show, and the gap between feeling and performance is one of the most consistent findings in this field.

• Self-report and objective tests disagree: Crawley, Dennison and Carter followed 15 pregnant and 14 non-pregnant women through pregnancy and the first year after birth. The two groups did not differ on objective tests of memory and attention, yet in the second trimester the pregnant women rated themselves as more impaired. The authors suggested that small lapses may be overcome by effort during a short test session, or that mood and expectations shape the self-ratings.

• Sleep and mood: Poor sleep and depression both lower scores on memory tasks and raise complaints about memory, and both are common in late pregnancy and the months after birth. Orchard's review notes that some studies find the cognitive differences disappear once sleep and mood are taken into account. Our article on how sleep affects cognitive performance covers the wider evidence on sleep and test performance.

• The stereotype itself: Pownall, Conner and Hutter tested whether reminding pregnant women of the "baby brain" stereotype would worsen their scores, an effect known as "stereotype threat." In two experiments with 364 and 409 women, the reminder made no difference. In the first study, pregnant women and new mothers did worse than never-pregnant women on memory; in the second, the groups did not differ.

• The comparison group: Many studies compare pregnant women with women who already have children. Orchard's review argues that this blurs any difference, since motherhood may itself have lasting effects on cognition, and recommends never-pregnant controls.

If memory problems are severe, appear suddenly or come with persistent low mood, that is worth raising with a midwife, obstetrician or family doctor, since mood disorders are common during pregnancy and after birth.

Large studies of middle-aged and older adults point, if anything, in the other direction. Using UK Biobank brain scans of 12,021 middle-aged women, de Lange and colleagues found that women who had given birth showed less evidence of brain aging than women who had not. In a cognitive analysis of 303,196 UK Biobank participants, Ning and colleagues found that parents of two or three children had faster reaction times and made fewer errors on a visual memory task than childless adults, and the differences were larger in men. Because fathers showed the same pattern without being pregnant, the authors concluded that the lifestyle that comes with raising children is the more likely explanation. Childless adults and parents also differ in health, income and education in ways no observational study fully removes.

No study has shown that it does. The only study to give pregnant women full IQ tests found that their scores rose with repeated testing, as the comparison group's did, with no difference after birth.

There is a modest average dip on memory and executive-function tasks, mostly in the third trimester, and most women report feeling foggier. The dip is much smaller than the complaints and may be partly explained by sleep loss and low mood.

Gray matter volume falls during pregnancy, especially in regions linked to social cognition, and some of the change lasts at least two years. Researchers interpret it as an adaptation to motherhood, and it has not been linked to lower intelligence.

The best prospective study found no lasting cognitive change after motherhood. Long-term studies of parents in middle age show equal or slightly better test scores than in childless adults.

Henry and Rendell's meta-analysis found that the same memory weaknesses seen in pregnancy also appear after birth. The IQ study found no difference in IQ between new mothers and never-pregnant women at the postpartum session.

Pregnancy changes the brain, and many women feel less sharp, especially late in pregnancy and in the early months with a newborn. The test evidence shows a modest, temporary dip on demanding memory tasks, no drop in IQ and no lasting decline. If you want to see where your reasoning ability stands once things settle down, an online IQ test built by psychometricians gives a fuller picture than a single memory task.

1. Christensen, H., Leach, L. S., & Mackinnon, A. (2010). Cognition in pregnancy and motherhood: Prospective cohort study. British Journal of Psychiatry, 196(2), 126-132. [doi.org/10.1192/bjp.bp.109.068635](. doi.org

2. Crawley, R. A., Dennison, K., & Carter, C. (2003). Cognition in pregnancy and the first year post-partum. Psychology and Psychotherapy: Theory, Research and Practice, 76(1), 69-84. [doi.org/10.1348/14760830260569265](. doi.org

3. Davies, S. J., Lum, J. A., Skouteris, H., Byrne, L. K., & Hayden, M. J. (2018). Cognitive impairment during pregnancy: A meta-analysis. Medical Journal of Australia, 208(1), 35-40. [doi.org/10.5694/mja17.00131](. doi.org

4. de Lange, A.-M. G., Kaufmann, T., van der Meer, D., Maglanoc, L. A., Alnæs, D., Moberget, T., Douaud, G., Andreassen, O. A., & Westlye, L. T. (2019). Population-based neuroimaging reveals traces of childbirth in the maternal brain. Proceedings of the National Academy of Sciences, 116(44), 22341-22346. [doi.org/10.1073/pnas.1910666116](. doi.org

5. Henry, J. D., & Rendell, P. G. (2007). A review of the impact of pregnancy on memory function. Journal of Clinical and Experimental Neuropsychology, 29(8), 793-803. [doi.org/10.1080/13803390701612209](. doi.org

6. Hoekzema, E., Barba-Müller, E., Pozzobon, C., Picado, M., Lucco, F., García-García, D., Soliva, J. C., Tobeña, A., Desco, M., Crone, E. A., Ballesteros, A., Carmona, S., & Vilarroya, O. (2017). Pregnancy leads to long-lasting changes in human brain structure. Nature Neuroscience, 20(2), 287-296. [doi.org/10.1038/nn.4458](. doi.org

7. Ning, K., Zhao, L., Franklin, M., Matloff, W., Batta, I., Arzouni, N., Sun, F., & Toga, A. W. (2020). Parity is associated with cognitive function and brain age in both females and males. Scientific Reports, 10, 6100. [doi.org/10.1038/s41598-020-63014-7](. doi.org

8. Orchard, E. R., Rutherford, H. J. V., Holmes, A. J., & Jamadar, S. D. (2023). Matrescence: Lifetime impact of motherhood on cognition and the brain. Trends in Cognitive Sciences, 27(3), 302-316. [doi.org/10.1016/j.tics.2022.12.002](. doi.org

9. Pietschnig, J., Penke, L., Wicherts, J. M., Zeiler, M., & Voracek, M. (2015). Meta-analysis of associations between human brain volume and intelligence differences: How strong are they and what do they mean? Neuroscience and Biobehavioral Reviews, 57, 411-432. [doi.org/10.1016/j.neubiorev.2015.09.017](. doi.org

10. Pownall, M., Conner, M., & Hutter, R. R. C. (2021). The effects of activating a "baby brain" stereotype on pregnant women's cognitive functioning. Journal of Applied Social Psychology, 51(8), 809-824. [doi.org/10.1111/jasp.12802](. doi.org

11. Pritschet, L., Taylor, C. M., Cossio, D., Faskowitz, J., Santander, T., Handwerker, D. A., Grotzinger, H., Layher, E., Chrastil, E. R., & Jacobs, E. G. (2024). Neuroanatomical changes observed over the course of a human pregnancy. Nature Neuroscience, 27(11), 2253-2260. [doi.org/10.1038/s41593-024-01741-0](. doi.org

12. Rutherford, M. D., & Anderson, M. V. (2020). Changes in intelligence across pregnancy and the postpartum period. Human Ethology, 35(1), 91-105. [doi.org/10.22330/he/35/091-105](. doi.org

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