Microplastics (MPs) are defined as plastic particles smaller than 5 mm. They have been found almost everywhere they have been searched for and recent discoveries have also demonstrated their presence in human placenta, blood, meconium, and breastmilk, but their location and toxicity to humans have not been reported to date. The aim of this study was twofold: 1. To locate MPs within the intra/extracellular compartment in human placenta. 2. To understand whether their presence and location are associated with possible structural changes of cell organelles. Using variable pressure scanning electron microscopy and transmission electron microscopy, MPs have been localized in ten human placentas. In this study, we demonstrated for the first time the presence and localization in the cellular compartment of fragments compatible with MPs in the human placenta and we hypothesized a possible correlation between their presence and important ultrastructural alterations of some intracytoplasmic organelles (mitochondria and endoplasmic reticulum). These alterations have never been reported in normal healthy term pregnancies until today. They could be the result of a prolonged attempt to remove and destroy the plastic particles inside the placental tissue. The presence of virtually indestructible particles in term human placenta could contribute to the activation of pathological traits, such as oxidative stress, apoptosis, and inflammation, characteristic of metabolic disorders underlying obesity, diabetes, and metabolic syndrome and partially accounting for the recent epidemic of non-communicable diseases.

The difficulty in the clinical diagnosis of labor is due to an evolutionary mismatch. The ability to hide the signs and symptoms of labor is an evolutionary trait that was once advantageous, but became maladaptive due to environmental changes. Prospective diagnosis of labor is not possible with certainty using only clinical criteria; however, by analyzing the urinary metabolome of women in labor, this diagnosis is likely possible in all cases. In this review, we explain why the two methods (clinical and metabolomic) differ in efficacy and sensitivity, and we try to fit this difference into an evolutionary framework that explains these discrepancies considering evolutionary mismatch. The study of metabolomics allows the truth to emerge from the past, and the diffusion of metabolomic techniques and their application to clinical reality in the form of POC (Point of Care) could change the management of labor and childbirth in the future.