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Maternal hypothyroidism in pregnancy affects math scores in offspring
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Children born to mothers who have low levels of free thyroxine during their pregnancy are more likely to perform poorly on math tests at age 5 years when compared with children born to mothers with normal thyroid hormone levels, according to research in European Journal of Endocrinology.
In a longitudinal study of 1,196 mother-child pairs from Amsterdam, researchers found that maternal hypothyroidism at the end of the first trimester of pregnancy increased the odds of offspring performing poorly on math tests, but not on language tests.
Anna M. E. Noten, of the department of pediatrics at VU University Medical Center in the Netherlands, and colleagues analyzed data from 1,196 mother-child pairs (mean age of mothers, 32 years) from the Amsterdam Born Children and Their Development Study. Researchers measured serum free T4 and thyroid-stimulating hormone in mothers at a median gestational age of 12.9 weeks, and assessed school performance of their children at age 5 years by obtaining math and language test scores from the Central Institute for Test Development. The researchers conducted inverse-probability weighted analysis due to the possibility of non-response bias.
Within the cohort, 118 mothers were considered to have hypothyroxinemia.
Martijn Finken
Researchers found that, after adjusting for maternal education, ethnicity, BMI and depressive symptomatology, children born to mothers with free T4 concentrations in the lowest 10% of distribution at the end of their first trimester had 1.61 times higher odds (95% CI, 1.05-2.47) of a subnormal score (in the lowest 50% of distribution) on a math test. After inverse-probability weighting, the odds ratio dropped to 1.48 (95% CI, 0.94-2.32). The children’s performance on language tests was not significant after adjustment, and researchers found no association between maternal TSH levels during pregnancy and academic performance in offspring.
“[The research] adds to previous observations showing that low thyroxine levels during pregnancy are associated with developmental delays in infancy, and lower IQ and reaction time performance in childhood,” Martijn Finken, MD, PhD, of VU University Medical Center in the Netherlands, told Endocrine Today. “With the current study, we show that this has implications for daily life, namely school performance.”
“It is possible that these children could benefit from hormonal supplements to boost their brain development in the womb,” Finken said. “Such treatment has been tried in the past but as yet has failed to improve cognitive ability.” – by Regina Schaffer
Disclosure: The researchers report no relevant financial disclosures.
Perspective
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Tim Korevaar, MD, MSc
Early pregnancy is a crucial timeframe during which maternal thyroid hormones pass the placenta and regulate various fetal brain developmental processes. Noten and colleagues investigated the association between early pregnancy maternal thyroid function and school performance in 5-year-old offspring. Their finding that low maternal free thyroxine (T4) levels were associated with an increased risk of subnormal arithmetic school performance fits well with previous studies showing a lower IQ and an increased risk for adverse neurodevelopmental outcomes, including attention-deficit/hyperactivity disorder and autism, in children from mothers with similarly low free T4 levels. The results of the current study also reemphasize the important role of free T4 measurement during pregnancy, since virtually all studies point out that low maternal free T4 levels are associated with offspring brain development outcomes, as opposed to the more commonly assessed maternal thyroid-stimulating hormone levels. This is one of the first studies that investigates school performance, and it is important to note that because of the relatively low number of participants and analyses that hint towards selective follow-up, replication of these results will be important. Interestingly, a recent Finnish study presented at the European Thyroid Association last year reported that offspring of mothers who were hyperthyroid during pregnancy had a poor performance, also specifically in mathematics (Pakkila F, et al. Eur Thyroid J. 2014:73–226). Taken together, this may suggest that specific parts of the brain associated with, for example, abstract thinking are more susceptible to both too low and too high levels of maternal free T4 during pregnancy.
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