Fig. 1

Schematic diagram of study. 309 pregnant people were recruited in the first trimester and 288 remained in the study and had data collected at the time of birth. Among these, 173 provided a cord blood sample for epigenetic analysis at delivery. 206 of these families also had PFAS measured on their first-trimester plasma samples. Analytes of 9 PFAS were measured (Additional file 1: Table S1). Two PFAS were dropped from analysis due to poor detection (> 80% of samples below the limit of detection, BLOD). Another two PFAS (PFUnDA and MeFOSAA) were converted into categorical variables, detected or not detected, due to their moderate detection (> 40% and < 80% of samples BLOD). Five PFAS (PFHxS, PFOS, PFOA, PFNA, PFDA) were treated as continuous concentration measures in analysis, with < 40% of samples BLOD. From dyads that had PFAS, 155 had EPIC data on total methylation, and 90 had 5-hydroxymethylcytosine (5-hmC)/5-methylcytosine (5-mC) EPIC data. For total methylation, 141 samples and 744,926 probes passed quality control (QC). For 5-hmC/5-mC, 70 samples and 528,389 probes passed QC and screening criteria. Abbreviations: 5-hmC: 5-hydroxymethylcytosine; 5-mC: 5-methylcytosine; BLOD: below the limit of detection; MeFOSAA: 2-(N-methyl-perfluorooctane sulfonamido) acetic acid; MMIP: Michigan Mother Infant Pairs; PFAS: per-/polyfluoroalkyl substances; PFHxS: perfluorohexanesulphonic acid; PFDA: perfluorodecanoic acid; PFNA: perfluorononanoic acid; PFOA: perfluorooctanoic acid; PFOS: perfluorooctanesulfonic acid; PFUnDA: perfluoroundecanoic acid; QC: quality control