Maternal Pre-Pregnancy BMI and Intelligence Quotient (IQ) in 5-Year-Old Children: A Cohort Based Study

Mette Bliddal,Ellen A Nøhr,Thorkild I A Sørensen,Ulrik S Kesmodel,Henrik Støvring,Jørn Olsen,Hanne-Lise F Eriksen,Kenji J Tsuchiya

doi:10.1371/journal.pone.0094498

Abstract

BackgroundAn association between maternal pre-pregnancy BMI and childhood intelligence quotient (IQ) has repeatedly been found but it is unknown if this association is causal or due to confounding caused by genetic or social factors.MethodsWe used a cohort of 1,783 mothers and their 5-year-old children sampled from the Danish National Birth Cohort. The children participated between 2003 and 2008 in a neuropsychological assessment of cognitive ability including IQ tests taken by both the mother and the child. Linear regression analyses were used to estimate the associations between parental BMI and child IQ adjusted for a comprehensive set of potential confounders. Child IQ was assessed with the Wechsler Primary and Preschool Scales of Intelligence – Revised (WPPSI-R).ResultsThe crude association between maternal BMI and child IQ showed that BMI was adversely associated with child IQ with a reduction in IQ of −0.40 point for each one unit increase in BMI. This association was attenuated after adjustment for social factors and maternal IQ to a value of −0.27 (−0.50 to −0.03). After mutual adjustment for the father's BMI and all other factors except maternal IQ, the association between paternal BMI and child IQ yielded a regression coefficient of −0.26 (−0.59 to 0.07), which was comparable to that seen for maternal BMI (−0.20 (−0.44 to 0.04)).ConclusionAlthough maternal pre-pregnancy BMI was inversely associated with the IQ of her child, the similar association with paternal BMI suggests that it is not a specific pregnancy related adiposity effect.

Highlights

Maternal pre-pregnancy obesity is associated with numerous neonatal adverse outcomes such as increased risk of fetal death, macrosomia, and birth complications [1,2]
A recent study, investigating predictors for childhood intelligence quotient (IQ), found maternal BMI to be negatively associated with child IQ – apparently independent of maternal IQ - and maternal BMI was a predictor of child IQ [17]
We found an inverse trend between both maternal and paternal BMI and maternal IQ and educational status

Summary

Introduction

Maternal pre-pregnancy obesity is associated with numerous neonatal adverse outcomes such as increased risk of fetal death, macrosomia, and birth complications [1,2]. High BMI has been associated with a low IQ in adults and children [9,10,11,12,13] and childhood IQ, as a measure of general cognitive ability, has been inversely associated with maternal pre-pregnancy BMI in some studies but not all [3,14,15,16]. An association between maternal pre-pregnancy BMI and childhood intelligence quotient (IQ) has repeatedly been found but it is unknown if this association is causal or due to confounding caused by genetic or social factors

Methods

Results

Conclusion