Impact of placental microplastics on birth anthropometrics: A cross-sectional study

Despite growing concern about microplastic contamination in human tissues, the relationship between placental microplastic exposure and fetal anthropometric outcomes remains unexplored. This study investigated associations between placental microplastic content and birth weight (BW), birth length (BL), and head circumference (HC), in a large prospective cohort in China. We recruited 1750 mother-infant pairs between 2022-2024. Placental tissues were collected immediately after delivery from maternal and fetal sides using strict contamination-prevention protocols. Microplastics were identified and quantified via laser direct infrared (LD-IR) chemical imaging. Associations between polymer-specific microplastics (PVC, PP, PBS, PET) and fetal growth were assessed using multivariable linear regression, sex-stratified analyses, and mixture models, including g-computation (g-comp), generalized weighted quantile sum regression (gWQS), and Bayesian kernel machine regression (BKMR). Median placental microplastic concentrations were 7.0, 5.0, 4.0, and 3.0 particles/10 g tissue for PVC, PP, PBS, and PET, respectively. Higher microplastic exposure was consistently associated with reduced BW, BL, and HC. Total MPs were linked to a 107.7 g decrease in BW (95 % CI: -138.87, -76.49; p < 0.001). Sex-stratified analyses showed stronger effects in male infants, particularly for BW (p-interaction = 0.04). Mixture analyses indicated cumulative negative effects across polymers. The g-comp approach estimated a BW reduction of -117.7 g (95 % CI: -155.3, -80.1) and a BL decrease of -0.89 cm (95 % CI: -1.20, -0.58). The gWQS model produced comparable estimates for BW (-100.9 g, 95 % CI: -146.2, -55.5) and BL (-0.96 cm, 95 % CI: -1.34, -0.58), while BKMR confirmed monotonic negative associations for BW, BL, and HC, with PBS and PP contributing most to the mixture effect. Placental microplastic exposure is associated with impaired fetal growth, with boys appearing more vulnerable. Future studies should investigate biological mechanisms and long-term outcomes.