PRESS RELEASE
EMBARGO 00.01 BST Wednesday 26 August 2015
Mother’s hormone levels predict child’s ability to do maths
Children born to mothers with low levels of thyroid hormones during pregnancy are 60 % more likely
to do badly in arithmetic tests when they reach school age as children born to mothers with normal
levels of the hormone; according to a study published today in the European Journal of Endocrinology.
Scientists have already found that relatively low levels of the thyroid hormone thyroxine in pregnant
women is linked to poor mental development in their children during infancy. However, until now it
has been unclear how this change would be reflected in the children’s performance at school.
Dr Martijn Finken and colleagues at the VU University Medical Centre in The Netherlands studied
1,196 healthy children from birth to age five. At 12 weeks of pregnancy, the team recorded levels of
maternal thyroxine. The team then looked at the children’s school test scores for language and
arithmetic at age five.
The study found that five year olds whose mothers had very low levels of thyroxine (within the lowest
10 % of the distribution) at the end of the first trimester of their pregnancy were almost twice (1.9
times) as likely to score a subnormal mark in an arithmetic test than children whose mothers had
normal thyroxine levels during early pregnancy. When the family background of these children and
their variation in health at birth were taken into account then this was reduced to 1.6 times – meaning
they were actually 60 % more likely to score a subnormal mark. The children’s performance in
language tests however was not affected. The performance of the child was based on how well they
did in the test compared to the rest of the class; a subnormal test performance was defined as coming
in the lower 50% of the class.
Lead author of the study Dr Martijn Finken said: “Whether these problems persist into adulthood
remains to be seen. We will continue to follow these children to answer this next big question.”
In the future, hormone tests could be used to identify children who will need extra help in
mathematics at school. “It is possible that these children could benefit from hormonal supplements
to boost their brain development in the womb” suggested Dr Finken. “Such treatment has been tried
in the past but as yet has failed to improve cognitive ability.”
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Abstract
Maternal hypothyroxinemia in early pregnancy and school performance in 5-year-old offspring
Anna Noten1, Eva Loomans2,3, Tanja Vrijkotte4, Peter van de Ven5, Paul van Trotsenburg6, Joost
Rotteveel1, Manon van Eijsden2,7, Martijn Finken1
1
Department of Pediatrics, VU University Medical Center, Amsterdam, 2Department of Epidemiology,
Documentation and Health Promotion, Public Health Service Amsterdam, Amsterdam, 3Department of
Developmental Psychology, Tilburg University, Tilburg, 4Department of Public Health, Academic Medial
Center, Amsterdam, 5Department of Epidemiology and Biostatistics, VU University Medical Center,
Amsterdam, 6Department of Pediatric Endocrinology, Emma Children’s Hospital, Academic Medical
Center, University of Amsterdam, Amsterdam, 7Department of Health Sciences, VU University,
Amsterdam.
Objective: Overt hypothyroidism in pregnant women is associated with a lower intelligence quotient
in their children. More recently, subtle decreases in maternal thyroid function have also been
associated with neurodevelopmental impairment in offspring. We tested the effect of
hypothyroxinaemia during early pregnancy on school performance.
Design: This was a longitudinal study that included the data of 1,196 mother-child pairs from the
Amsterdam Born Children and their Development study.
Methods: Maternal serum free T4 and TSH were obtained at a median gestational age of 12.9
(interquartile range: 11.9-14.3) weeks. School performance was assessed at age 5 years and based on
scores obtained in arithmetics and language tests from the national monitoring and evaluation
system. Poor school performance was defined as a test result <25th percentile and subnormal school
performance as a result <50th percentile of the norm population. To estimate the impact of possible
non-response bias, we conducted inverse-probability weighted analyses.
Results: Maternal hypothyroxinaemia (i.e., a maternal free T4 in the lowest 10% of distribution) was
associated with a 1.61 (95% confidence interval (CI): 1.05-2.47) –fold increased odds of subnormal
arithmetic performance after adjustment for confounders (p= 0.03). However, the odds ratio dropped
to 1.48 (95% CI: 0.94-2.32) after inverse-probability weighting (p= 0.09). No such relations were found
with TSH.
Conclusions: Maternal hypothyroxinemia at the end of the first trimester was associated with reduced
performance in an arithmetics test, but not in a language test, in 5-year-old offspring. However, our
results should be interpreted carefully, because of possible non-response bias.
Notes for Editors
1. For further information about the study please contact:
J. Spee or M. Hossteenge
Department of Communication
VU University Medical Center
De Boelelaan 1117
1081HV
Amsterdam
Tel: +31 (0)204 443444
Email: communicatie@vumc.nl
2. The study “Maternal hypothyroxinemia in early pregnancy and school performance in 5year-old offspring” will be published in the European Journal of Endocrinology on Wednesday
26 July 2015. For copies of the study, please contact the press office using the details below.
3. For other press enquiries, or copies of the abstract, please contact the Bioscientifica press
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