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

• Published in: PloS one 2012-12, Vol.7 (12), p.e51084-e51084
• Main Authors: Bonilla, Carolina, Lawlor, Debbie A, Taylor, Amy E, Gunnell, David J, Ben-Shlomo, Yoav, Ness, Andrew R, Timpson, Nicholas J, St Pourcain, Beate, Ring, Susan M, Emmett, Pauline M, Smith, A David, Refsum, Helga, Pennell, Craig E, Brion, Marie-Jo, Smith, George Davey, Lewis, Sarah J
• Format: Article
• Language: English
• Subjects: Adult; Biology; Blood; Brain; Child; Children; Children & youth; Cognitive ability; Confounding Factors, Epidemiologic; Correlation analysis; Dietary Supplements; Epidemiology; Ethics; Female; Fetal Blood - metabolism; Genetic Association Studies; Genomes; Haplotypes; Homocysteine; Humans; Intelligence; Intelligence Tests; Longitudinal Studies; Male; Mediation; Medicine; Mendelian Randomization Analysis; Nervous system; Offspring; Parents; Parents & parenting; Polymorphism, Single Nucleotide - genetics; Population; Pregnancy; Pregnant women; Principal components analysis; Progeny; Single nucleotide polymorphisms; Single-nucleotide polymorphism; Studies; United Kingdom; Vitamin B; Vitamin B 12 - blood; Vitamin deficiency; Vitamins; Womens health
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0051084

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.