Association between phthalate metabolites in human amniotic fluid and offspring birth size: a sub-study of the PERSIAN birth cohort

Abstract

As phthalate metabolites might cross the placenta, it is possible to find them in the amniotic fluid. This cross-sectional study aims to investigate the levels of phthalate metabolites in the amniotic fluid of a sample of Iranian women and its association with neonatal anthropometric measures. The other objective was to study the potential sources of maternal exposure to phthalates. This study was conducted from June 2019 to June 2021 in Isfahan, Iran. Pregnant women were recruited from their first trimester of pregnancy and followed up until their delivery. Amniotic fluid samples were collected from those who were assigned to have delivery by cesarean section. Overall, 158 samples of amniotic fluid were collected, of which 139 samples had sufficient volume and were free of blood. Data from 142 newborns were included in this study. Four phthalate metabolites were measured using gas chromatography-mass spectrometry (GC-MS). After extraction of phthalate metabolites, 4 phthalate metabolites including mono-butyl phthalate (MBP; normal: 0.08 ± 0.79; overweight: 0.20 ± 1.11; obese: 0.07 ± 1.07; p-value: 0.405), mono-benzyl phthalate (MBzP; normal: 7.54 ± 6.69; overweight: 7.48 ± 7.16; obese: 8.67 ± 12.75; p-value: 0.729), mono(2-ethyl-5-oxohexyl) phthalate (MEOHP; normal: 4.27 ± 6.36; overweight: 3.03 ± 8.44; obese: 3.53 ± 7.04; p-value: 0.245), and mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP; normal: 246.18 ± 189.80; overweight: 238.48 ± 200.23; obese: 287.65 ± 206.70; p-value: 0.723) were simultaneously detected in samples of maternal amniotic fluid. Our findings suggest that maternal exposure to phthalate metabolites is positively associated with in utero exposure of the developing fetus. The geometric means and medians of MBP, MBzP, MEOHP, and MEHHP of detected samples were 10.17 (9.52), 6.24 (3.47), 5.03 (11.72), and 174.79 (229.94) (μg/L), respectively. The median anthropometric measures of newborns were as follows: weight 3171.8 g, height 49.6 cm, head circumferences 34.9 cm, chest 33.3 cm, hip 31.5 cm, and arm circumferences 10.8 cm. There was no statistically significant association between phthalate metabolites concentration and newborn's anthropometric measures (p > 0.05). Future studies should focus on the collection of amniotic fluid at different trimesters and the corresponding maternal samples to better characterize the association and health impacts of these endocrine-disrupting chemicals during fetal development.