Is meconium useful to predict fetal exposure to organochlorines and hydroxylated PCBs?

The objective of this study is to compare meconium and maternal serum as biomarkers of fetal exposure to organochlorines (OCs). A subset of 40 meconium samples and complementary maternal sera from the Northern Norway Mother-and-Child Contaminant Cohort Study (MISA) were selected. Meconium samples were collected at the earliest opportunity (median 9.0 hours postpartum, range 0-61) and maternal serum in the 2nd trimester (median 19.0 gestational weeks, range 13-34) and analysed for OC contaminants selected from the Arctic Monitoring and Assessment Programme's (AMAP) suite of OCs and selected hydroxylated metabolites. Eight compounds with detection frequencies ≥70% in both media (criterion for inclusion) were included in the statistical analyses. Median concentration ratios for p,p'-DDE, HCB, trans-nonachlor and cis-nonachlor favoured meconium, and PCB 138 and 153 and OH-PCB 146 and 172 were higher in maternal serum. All inter-media correlations were significant (Spearman's rho) for wet-weight concentrations and improved when concentrations in a small subset of 15 meconium and serum samples were both lipid-adjusted; only OH-PCB 146 slightly favoured maternal serum. Multivariable linear regression modelling confirmed that maternal serum was the most consistent predictor of meconium concentrations, with gestational age and time of meconium sampling improving the models. Although more challenging to analyse, the lipid-adjusted OC concentration in meconium is viewed as a sensitive and informative fetal exposure index when taking into account the gestational age and its postpartum sampling time.