Effects of the phthalate exposure during three gestation periods on birth weight and their gender differences: A birth cohort study in China

Highlights: • This study used repeated measurement data from a large birth cohort and explored the effect by mixed linear model. • This study showed the effect of prenatal phthalate exposure was sex specific and male infants were more sensitive. • This study found the effect in low and high birth weight infants was stronger than normal birth weight infants. Phthalate has been widely used as a type of plasticiser in various consuming products in daily life. Recent studies have suggested that prenatal phthalate exposure may have adverse effects on fetal development. We aimed to identify the effects of in utero phthalate exposure on birth weight (BW). We evaluated a birth cohort comprising 3474 pregnant women and their single infants; 3103, 2975 and 2838 urine samples were collected in the first, second and third trimesters, respectively. Phthalate metabolites included monomethyl phthalate (MMP), monoethyl phthalate (MEP), mono-n-butyl phthalate (MBP), monobenzyl phthalate (MBzP), mono-(2-ethylhexyl) phthalate (MEHP), mono-(2-ethyl-5-oxohexyl) phthalate (MEHHP), and mono-(2-ethyl-5-hydroxylhexyl) phthalate (MEOHP), which were analysed in the urine by using high performance liquid chromatography–tandem mass spectrometry. Mixed linear model was used in the statistical analysis. Generally, MMP and MEP exposure during pregnancy was associated with decreased birth weight of infants (MMP, β = − 12.192, p = 0.009; MEP, β = − 11.876, p = 0.014). Hierarchical analysis found that MMP and MEOHP exposure was associated with decreased infants' birth weight only in low birth weight groups (MMP, β = − 42.538, p = 0.005; MEOHP, β = − 63.224, p = 0.008); MEHP and MEHHP exposure was associated with decreased infants' birth weight in both low birth weight group (MEHP, β = − 42.348, p = 0.035; MEHHP, β = − 50.485, p = 0.006) and high birth weight group (MEHP, β = − 16.580, p = 0.034; MEHHP, β = − 18.009, p = 0.040), MBP and MEHP exposure were associated with increased infants' birth weight in male NBW group (MBP, β = 10.438, p = 0.039; MEHP, β = 13.223, p = 0.017). Moreover, the effect has sex difference. The reduction of birth weight associated with MEHP and MEOHP exposure was stronger in male infants, while MMP and MEP exposure was more significant in female infants.