Year 116 of the plastic age: a Pandora's box as a time bomb for pregnancy? Review of clinical and fundamental data on prenatal exposure to plastics.

Plastics constitute an area of interest within the context of the placental exposome. A growing body of evidence now indicates that various micro- and nanoplastics - including notably polystyrene, polypropylene, polyethylene, and polyvinylchloride - are present in the human placenta, from the basal plate to the fetal membranes. Results from in vitro and ex vivo studies have shown that these environmental pollutants can enter the maternal bloodstream and reach the placenta, where they concentrate in the syncytiotrophoblast. These so-called "plasticenta" have been observed even in uncomplicated pregnancies, and to date, no longitudinal study has confirmed harmful long-term consequences for the newborn. However, plastics appear to alter placental functions and may therefore be associated with adverse outcomes such as miscarriage, intrauterine growth restriction and preterm birth. Findings from ex vivo human studies, in vivo murine models, and in vitro experiments with micro- and nanoplastics indicate that factors such as particle type, size, concentration, surface functionalization, route of exposure, and environmental conditions play key roles in cellular uptake and subsequent alterations in cell function and phenotype. Consequently, various impairments in placental metabolic and immune functions may contribute to abnormal development of the placenta and the fetus. Maternal exposure to these ubiquitous environmental pollutants may induce prenatal and neonatal disease states. In this review, we examine the current clinical, in vivo and in vitro data on the occurrence, distribution and impact of micro- and nanoplastics in the placenta.