Sex-specific associations between prenatal exposure to environmental pollutants and birth outcomes: a meconium biomonitoring study

Prenatal exposure to environmental pollutants, particularly heavy metals and pesticides, is a major public health concern because of its potential association with fetal growth and development. These toxicants can cross the placental barrier and accumulate in fetal tissues. Meconium, the first neonatal feces, is a well-established biomarker of cumulative fetal exposure during late pregnancy. However, evidence regarding sex-specific associations between prenatal pollutant exposure and neonatal outcomes remains limited, particularly in low- and middle-income countries. A cross-sectional study was conducted among 123 full-term newborns in Syria between August and September 2025, including 68 from Damascus and 55 from Latakia. Meconium samples were collected within the first hours after birth, prior to feeding, using sterile contamination-free procedures. Samples were stored at - 20 °C and transported under controlled cold-chain conditions to accredited laboratories. Heavy metals (Pb, Hg, Cd, As, Cr, Ni, Mn, Cu, Se, Tl, Sb) were quantified using atomic absorption spectrophotometry following microwave-assisted acid digestion. Pesticides (diazinon, chlorpyrifos, malathion, DDT/DDE, permethrin) were extracted using organic solvents and analyzed using high-performance liquid chromatography. Statistical analyses were performed using SPSS version 23.0, including sex-stratified multivariate regression models adjusted for maternal and neonatal covariates. All target pollutants were detected in meconium samples, indicating widespread prenatal exposure. Considerable inter-individual variability in pollutant concentrations was observed across all analytes. Sex-specific associations were identified between pollutant levels and neonatal outcomes. Among male newborns, mercury was negatively associated with birth weight, whereas nickel showed a positive association. Diazinon exposure was associated with reduced head circumference. Among female newborns, lead, thallium, and DDT/DDE showed associations with birth weight. In addition, DDT/DDE was associated with head circumference and birth length, whereas permethrin was associated with shorter birth length. Descriptive regional variation in pollutant concentrations was observed between Damascus and Latakia, although these differences were not the primary focus of the present analysis. This study identified widespread prenatal exposure to multiple environmental pollutants and observed sex-specific associations with neonatal outcomes. Meconium biomonitoring represents a useful approach for assessing cumulative fetal exposure during late pregnancy. Given the observational cross-sectional design, these findings should be interpreted cautiously. Some pesticide-related findings require confirmation using more selective analytical methods. Further prospective studies are needed to confirm these associations and better understand the biological mechanisms underlying sex-specific susceptibility.