Effect modification by maternal vitamin D status in the association between prenatal exposure to per- and polyfluoroalkyl substances and neurodevelopment in 2-year-old children

[Display omitted] •Pregnant women in SBC faced the dual threats of PFAS exposure and VD insufficiency.•Different PFAS levels between VD groups may confound the effect estimates.•We balanced the effects of different PFAS levels between VD groups by matching.•Combined high PFAS and low VD in mothers would exacerbate childhood neurodevelopment.•Nutrition should be involved to combat the hazards of environmental pollutants. Pregnant women in the Shanghai Birth Cohort (SBC) of China faced dual threats of per- and polyfluoroalkyl substances (PFAS) exposure and vitamin D (VD) insufficiency, potentially impacting offspring neurodevelopment. However, little is known about whether maternal VD status modifies PFAS-related neurodevelopment effect. To explore the modifying role of maternal VD status in the effect of prenatal PFAS exposure on childhood neurodevelopment. We included 746 mother–child pairs from the SBC. Ten PFAS congeners and VD levels were measured in maternal blood samples collected during the first and second trimester respectively. At 2 years of age, toddlers underwent neurodevelopment assessments using Bayley-III Scales. Multivariate linear, logistic regression, and weighted quantile sum approach were used to estimate associations of Bayley-III scores with individual and mixture PFAS. We stratified participants into VD sufficient and insufficient groups and further balanced PFAS differences between these groups by matching all PFAS levels. We fitted the same statistical models in each VD group before and after matching. Nearly half (46.5 %) of pregnant women were VD insufficient (