Lower Maternal Serum Folate in First Trimester Associated with Higher Autism Risk in Offspring

Abstract

BackgroundEpidemiologic evidence suggests that periconceptional maternal folate intake is associated with decreased risk for autism spectrum disorder (ASD), but the biochemical underpinnings of this relationship and direct maternal folate measurement have not been reported.ObjectiveTo examine the association between first trimester in utero maternal metabolic risk factors (including methyl donors and folate metabolites, markers of oxidative stress and inflammation, and maternal BMI) and risk of ASD at age 4–7years.MethodsUsing a case‐control design, we identified 44 four to seven year old children with an ADOS‐confirmed diagnosis of Autism Spectrum Disorder treated at Maine Medical Center Developmental Behavioral Pediatrics Clinic (Portland, ME). Archived maternal blood samples from the first trimester of pregnancy (11–13 weeks gestational age) were identified for these cases at the Foundation for Blood Research in Scarborough, ME. 44 control samples from the biorepository were identified based on five matching criteria (sex of child, maternal age, maternal smoking status, age of sample, gestational age of sample collection.) All samples were linked with birth certificate data to identify covariates. We measured unmetabolized folic acid (FA), 5‐methyl tetrahydrofolate (MTHF), vitamin B12, homocysteine and high Sensitivity C Reactive protein (CRP) from the samples. We examined the associations between these factors in pregnancy and diagnosis of ASD with logistic regression using SAS version 9.2.ResultsMaternal and infant characteristics for cases and controls are shown in table 1. Although in other cohorts maternal obesity has been associated with increased risk of ASD, maternal obesity was not associated with ASD diagnosis in our cohort, although our power for this comparison was low. As shown in table 2, maternal first trimester serum concentration of 5‐MTHF in the lower 2 tertiles (T1, T2) (compared to the highest tertile, T3) was associated with increased odds of ASD diagnosis in offspring [OR (95% CI) T1: 6.04 (1.25, 29.30) and T2: 7.10 (1.38, 36.46)]. Maternal CRP, FA, vitamin B12, and homocysteine were not significantly associated with risk of ASD (Table 2).ConclusionsLower first trimester serum maternal 5‐MTHF concentration was associated with increased risk of developing autism in offspring in an unadjusted analysis. Analysis of markers of oxidative stress and products of folate catabolism in these samples as well as adjustment for potential confounders is underway. If these findings are confirmed in larger cohorts, this may present an opportunity for prenatal intervention to reduce the risk for autism.Support or Funding InformationThe Alden Trust Characteristics of mother‐infant pairs of ASD cases and controls. Characteristic Cases (n= 44) Controls (n= 44) p n (%) Mother's BMI at blood draw <25 kg/m2 14 (32%) 17 (39%) 0.61 25–<30 kg/m2 12 (27%) 14 (32%) 30–<35kg/m2 7 (16%) 9 (20%) 35+ kg/m2 11 (25%) 4 (9%) Gestational age at birth <37 weeks 7 (16%) 6 (14%) 0.43 37–40 weeks 36 (82%) 33 (75%) >40 weeks 1 (2%) 5 (11%) Maternal tobacco use No 35 (81%) 36 (83%) 0.32 Yes 8 (19%) 7 (17%) Unknown 1 1 Gestational diabetes No 42 (95%) 43 (98%) 0.56 Yes 2 (5%) 1 (2%) Maternal Education HS or less 13 (30%) 11 (25%) 0.26 Some college or degree 22 (50%) 22 (50%) Post college 9 (20%) 11 (25%) Paternal Education HS or less 13 (52%) 8 (32%) 0.09 Some college or degree 4 (16%) 11 (44%) Post college 8 (32%) 6 (24%) Missing 18 16 Mother's Race/ethnicity Black 2 (5%) 0 (0%) White 40 (91%) 43 (98%) Asian 2 (5%) 1 (2%) Gestational Age at blood draw (wks) 11 12 (27%) 10 (23%) 0.57 12 18 (41%) 18 (41%) 13 14 (32%) 16 (36%) Year of blood draw 2008 9 (20%) 8 (18%) 0.90 2009 11 (25%) 12 (27%) 2010 16 (36%) 14 (32%) 2011 8 (18%) 10 (23%) Infant Male Sex 30 (68%) 30 (68%) 1.00 Odds ratios (OR) and 95% CIs for associations between first trimester maternal metabolic markers and ASD diagnosis at 4–7 years compared to controls. Maternal Metabolic Marker OR (95% CI) Unmetabolized Folic Acid (FA) nmol/L <0.293 1.06 (0.36, 3.13) 0.293–<1.89 1.28 (0.40, 4.08) 1.89+ 1.00 (Referent) Serum 5‐Methyl THF nmol/L <19.3 6.04 (1.25, 29.30) 19.3–<27.4 7.10 (1.38, 36.46) 27.4+ 1.00 (Referent) Serum Vitamin B12 pg/ml <450 0.74 (0.25, 2.18) 450–<702 0.72 (0.26,1.96) 702+ 1.00 (Referent) Homocysteine micromol/L <3.09 0.65 (0.22, 1.96) 3.09–<3.68 1.25 (0.41, 3.81) 3.68+ 1.00 (Referent) Serum High Sensitivity CReactive protein (CRP) mg/L <1.7 1.00 (Referent) 1.7–<7.2 0.84 (0.29, 2.47) 7.2+ 0.68 (0.20, 2.32)