Maternal Age and IQ: Do Older Mothers Have Smarter Children?

Children born to older mothers score slightly higher on cognitive tests today: in a UK cohort born in 2000 to 2002, children of mothers aged 35 to 39 scored 0.16 standard deviations, roughly 2.4 IQ points, higher at age 10 or 11 than children of mothers aged 25 to 29. Studies that compare siblings born to the same mother at different ages find that the mother's age itself does little, and may even cost about 1 point, so the advantage reflects which women become mothers later.

This page covers what the large birth cohorts show and why the direction of the link reversed over time, what happens when researchers compare brothers and sisters, what the evidence says about teenage mothers, and how birth order, education and the rising scores of each generation get tangled up with a mother's age.

The most informative single study is by Alice Goisis, Daniel Schneider and Mikko Myrskylä, who compared three British birth cohorts born in 1958 (10,969 children), 1970 (9,362) and 2000 to 2002 (11,600). Each child took cognitive tests at age 10 or 11, and the scores were converted to "standard deviation" units, a measure of spread in which one unit equals 15 points on a typical IQ scale.

In the two older cohorts, children of mothers aged 35 to 39 scored slightly lower than children of mothers aged 25 to 29 (-0.06 standard deviations in 1958 and -0.12 in 1970, or about 1 to 2 IQ points). In the 2000 to 2002 cohort, the sign flipped to +0.16, about 2.4 points. Mothers aged 40 and over showed a similar pattern. The authors traced the reversal to who older mothers were. In the earlier cohorts, older mothers were usually having later children in larger families. By 2000, they were more likely to come from socioeconomically advantaged backgrounds.

A large US dataset points the same way. Sukanta Saha and colleagues analyzed 33,437 children from the Collaborative Perinatal Project, tested at 8 months, 4 years and 7 years. Older fathers were linked to slightly lower scores, while older mothers were generally linked to better scores. When Ryan Edwards and Jennifer Roff reanalyzed the same project, adding the mother's education and the number of siblings made the father's age effect statistically insignificant for most measures. The authors attributed this to assortative mating, the tendency of partners to resemble each other, and that kind of overlap runs through this whole literature.

The strongest test of whether a mother's age matters is to compare children born to the same mother at different ages. Siblings share their parents' education, income and much of their genes, so any remaining difference is closer to the effect of age itself.

Mikko Myrskylä, Karri Silventoinen, Per Tynelius and Finn Rasmussen did this with 565,433 Swedish men born from 1951 to 1976, whose IQ was measured at military conscription between ages 17 and 20. Their method accounted for the fixed characteristics that brothers share. After adjusting for birth year, maternal ages above 30 were linked to slightly lower IQ: sons born when their mother was 40 to 44 scored 0.07 standard deviations (about 1 point) lower than sons born when she was 25 to 29. Without that adjustment, older maternal age was linked to higher IQ, because a later-born child grows up in a later generation, and test scores were rising from one birth year to the next (the "Flynn effect"). The rising scores more than offset the small within-family cost.

A Swedish register study of 943,444 men published in 2026 by Vasudha Ahuja and colleagues found the same reversal. In standard comparisons, sons of mothers aged 36 or older scored higher on the conscription cognitive test than sons of mothers aged 16 to 25. In sibling comparisons, the sign reversed and the later-born brothers scored lower. A methods paper by David Carslake and colleagues, using data on up to 3.65 million Swedish offspring, found that the offspring of older mothers had higher intelligence in standard analyses, and warned that sibling comparisons are driven largely by birth date when an outcome is changing over time, as IQ scores were.

Sibling comparisons have a built-in complication. The younger sibling is born when the mother is older, so maternal age and birth order move together, and firstborns tend to score slightly higher than their younger siblings. Our page on IQ and birth order covers that effect. Separating the two requires large samples and careful models, which is why the within-family estimates are small and somewhat uncertain.

Children of very young mothers score lower on average, and here too, sibling designs suggest that family circumstances do most of the work. In the 2026 Swedish study, sons of mothers who gave birth before age 16 scored lower on the conscription cognitive test than sons of mothers aged 16 to 25. When the authors compared those sons with brothers born when the same mother was older, the difference attenuated to null.

Two US studies point in a similar direction with school outcomes. Greg Duncan and colleagues, using the Children of the National Longitudinal Survey of Youth, found that each year a mother delayed her first birth was linked to 0.02 to 0.04 standard deviations higher school achievement at ages 10 to 13, results fairly robust to sibling and cousin comparisons. The main pathway was that delaying a first birth allowed mothers to complete more schooling. Samuel Fishman and Stella Min, using the Add Health study, found that the link between maternal age and offspring education largely reflected which women had children at which ages, with early teenage childbearing as the exception. Neither study measured IQ directly, and achievement and IQ are related but different.

The idea that older mothers have smarter children rests on real correlations in recent cohorts. Women who delay childbirth in high-income countries today are more likely to have university degrees and higher incomes, and both predict children's scores. A mother's own IQ is a further confounder, because it predicts both when she has children and her child's IQ. The same problem affected early research on breastfeeding, which we discuss in our page on IQ and breastfeeding.

• Education and income: In the UK cohorts, the shift from a negative to a positive link was explained by older mothers becoming more socioeconomically advantaged.

• Birth order: Older mothers in past generations were more often having later-born children, who score slightly lower on average.

• Generational score gains: A child born later belongs to a later birth cohort, and rising test scores can make a mother's age look beneficial when it is not.

• Fathers' age: Older mothers tend to have older partners, so studies of either parent's age need to adjust for the other.

Older maternal age does carry separate, well-established risks that are a different question from IQ. The chance of having a child with Down syndrome increases as a woman gets older, according to the National Library of Medicine. For low birth weight and preterm birth, a Finnish within-family study of 124,098 children found that the higher risk seen at ages 35 and over was negligible once siblings were compared. Anyone weighing these risks for a pregnancy should speak with an obstetrician or a genetic counselor.

In recent cohorts, children of mothers in their late 30s score about 2 IQ points higher on average. Sibling studies suggest this reflects the mother's education and circumstances rather than her age, and within families a later birth is linked to a slightly lower score.

The direct effect appears small. In a study of 565,433 Swedish men, sons born when their mother was 40 to 44 scored about 1 point lower than brothers born when she was 25 to 29.

They score lower on average. A Swedish sibling study found that the gap for mothers under 16 attenuated to null when brothers born at different maternal ages were compared, pointing to family circumstances.

Some studies link older fathers to slightly lower childhood scores. A reanalysis of one large US dataset found that the effect largely disappeared once the mother's education and the number of siblings were taken into account.

The evidence does not identify one. Within families, maternal age has only a small effect on IQ, and decisions about timing involve many other factors best discussed with a clinician.

The link between maternal age and IQ has changed sign over time. In Britain, children of mothers in their late 30s scored slightly lower in the 1958 and 1970 cohorts and about 2.4 points higher in the 2000 to 2002 cohort, because older mothers became better educated and better off. When siblings are compared, the mother's age itself has a small effect, about 1 point for the oldest mothers, and the advantage of later-born generations outweighs it. If you want a careful measure of your own reasoning abilities, you can try an online IQ test built by psychometricians.

1. Goisis, A., Schneider, D. C., & Myrskylä, M. (2017). The reversing association between advanced maternal age and child cognitive ability: Evidence from three UK birth cohorts. International Journal of Epidemiology, 46(3), 850-859. [doi.org/10.1093/ije/dyw354](. doi.org

2. Saha, S., Barnett, A. G., Foldi, C., Burne, T. H., Eyles, D. W., Buka, S. L., & McGrath, J. J. (2009). Advanced paternal age is associated with impaired neurocognitive outcomes during infancy and childhood. PLoS Medicine, 6(3), e1000040. [doi.org/10.1371/journal.pmed.1000040](. doi.org

3. Edwards, R. D., & Roff, J. (2010). Negative effects of paternal age on children's neurocognitive outcomes can be explained by maternal education and number of siblings. PLoS ONE, 5(9), e12157. [doi.org/10.1371/journal.pone.0012157](. doi.org

4. Myrskylä, M., Silventoinen, K., Tynelius, P., & Rasmussen, F. (2013). Is later better or worse? Association of advanced parental age with offspring cognitive ability among half a million young Swedish men. American Journal of Epidemiology, 177(7), 649-655. [doi.org/10.1093/aje/kws237](. doi.org

5. Ahuja, V., Hiyoshi, A., Backman, H., Simmons, D., & Montgomery, S. (2026). Peripubertal pregnancies and associations with health and developmental outcomes in offspring during late adolescence and adulthood: Sibling-comparison register study. International Journal of Epidemiology, 55(5), dyag153. [doi.org/10.1093/ije/dyag153](. doi.org

6. Carslake, D., Tynelius, P., van den Berg, G., Davey Smith, G., & Rasmussen, F. (2017). Associations of parental age with health and social factors in adult offspring. Methodological pitfalls and possibilities. Scientific Reports, 7(1), 45278. [doi.org/10.1038/srep45278](. doi.org

7. Duncan, G. J., Lee, K. T. H., Rosales-Rueda, M., & Kalil, A. (2018). Maternal age and child development. Demography, 55(6), 2229-2255. [doi.org/10.1007/s13524-018-0730-3](. doi.org

8. Fishman, S. H., & Min, S. (2018). Maternal age and offspring's educational attainment. Journal of Marriage and Family, 80(4), 853-870. [doi.org/10.1111/jomf.12490](. doi.org

9. MedlinePlus Genetics. (n.d.). Down syndrome. National Library of Medicine. [medlineplus.gov](. medlineplus.gov

10. Goisis, A., Remes, H., Barclay, K., Martikainen, P., & Myrskylä, M. (2017). Advanced maternal age and the risk of low birth weight and preterm delivery: A within-family analysis using Finnish population registers. American Journal of Epidemiology, 186(11), 1219-1226. [doi.org/10.1093/aje/kwx177](. doi.org

Hero image: Hands on baby, by chelly cruz, CC BY-SA 2.0. Via Wikimedia Commons.