Association between placental microplastic burden and intrapartum fetal heart rate abnormalities

Microplastic (MP) contamination has emerged as a global environmental concern, with increasing evidence of its presence in human placental tissue. However, no previous human studies have directly evaluated the association between placental microplastic exposure and fetal cardiac physiology during labor. Our study aimed to investigate the relationship between placental MP accumulation and the occurrence of intrapartum non-reassuring fetal heart rate (NRFHR). A prospective cohort study was conducted among 2738 pregnant women recruited from China between 2023 and 2024. Placental MPs were quantified using laser direct infrared (LD-IR) chemical imaging, focusing on polyvinyl chloride (PVC), polypropylene (PP), polyethylene terephthalate (PET), and polybutylene succinate (PBS). Multivariable logistic regression models were used to examine associations between placental MP concentrations and NRFHR, adjusting for maternal, socioeconomic, and pregnancy-related covariates. Stratified analyses, mixture models using quantile g-computation (g-comp) and generalized weighted quantile sum (gWQS), and sensitivity analyses were also performed. The median total placental MP concentration was 22 particles/10 g tissue (IQR: 11), with PVC showing the highest concentrations. Higher placental concentrations of PVC, PBS, PET, and total MPs were significantly associated with higher odds of NRFHR. In adjusted models, each IQR increase in PVC, PBS, PET, and total MPs was associated with 33% (OR: 1.33, 95% CI: 1.08-1.64), 80% (OR: 1.80, 95% CI: 1.44-2.25), 40% (OR: 1.40, 95% CI: 1.14-1.73), and 47% (OR: 1.47, 95% CI: 1.25-1.74) higher odds of NRFHR, respectively. Mixture analyses confirmed a significant positive joint effect of placental MPs on NRFHR, with PBS and PET contributing most strongly. Associations were more pronounced among pregnancies with environmental tobacco exposure. Placental microplastic exposure was associated with a higher risk of NRFHR, suggesting that prenatal MP accumulation may adversely affect fetal cardiac regulation during labor.