PLoS ONE (Jan 2012)

Vitamin B-12 status during pregnancy and child's IQ at age 8: a Mendelian randomization study in the Avon longitudinal study of parents and children.

  • Carolina Bonilla,
  • Debbie A Lawlor,
  • Amy E Taylor,
  • David J Gunnell,
  • Yoav Ben-Shlomo,
  • Andrew R Ness,
  • Nicholas J Timpson,
  • Beate St Pourcain,
  • Susan M Ring,
  • Pauline M Emmett,
  • A David Smith,
  • Helga Refsum,
  • Craig E Pennell,
  • Marie-Jo Brion,
  • George Davey Smith,
  • Sarah J Lewis

DOI
https://doi.org/10.1371/journal.pone.0051084
Journal volume & issue
Vol. 7, no. 12
p. e51084

Abstract

Read online

Vitamin B-12 is essential for the development and maintenance of a healthy nervous system. Brain development occurs primarily in utero and early infancy, but the role of maternal vitamin B-12 status during pregnancy on offspring cognitive function is unclear. In this study we assessed the effect of vitamin B-12 status in well-nourished pregnant women on the cognitive ability of their offspring in a UK birth cohort (ALSPAC). We then examined the association of SNPs in maternal genes FUT2 (rs492602) and TCN2 (rs1801198, rs9606756) that are related to plasma vitamin B-12, with offspring IQ. Observationally, there was a positive association between maternal vitamin B-12 intake and child's IQ that was markedly attenuated after adjustment for potential confounders (mean difference in offspring IQ score per doubling of maternal B-12 intake, before adjustment: 2.0 (95% CI 1.3, 2.8); after adjustment: 0.7 (95% CI -0.04, 1.4)). Maternal FUT2 was weakly associated with offspring IQ: mean difference in IQ per allele was 0.9 (95% CI 0.1, 1.6). The expected effect of maternal vitamin B-12 on offspring IQ, given the relationships between SNPs and vitamin B-12, and SNPs and IQ was consistent with the observational result. Our findings suggest that maternal vitamin B-12 may not have an important effect on offspring cognitive ability. However, further examination of this issue is warranted.