Prenatal Microplastic Exposure and Congenital Structural Anomalies in Humans: A Scoping Review

This project is a scoping review entitled **“Prenatal Microplastic Exposure and Congenital Structural Anomalies in Humans: A Scoping Review.”** The review aims to systematically map the extent, characteristics, and nature of the available peer-reviewed human evidence concerning prenatal exposure to microplastics and congenital structural anomalies. Microplastics have increasingly been detected in human biological samples relevant to pregnancy and fetal development, including the placenta, amniotic fluid, umbilical cord blood, meconium, and fetal tissues and organs. These findings indicate that microplastics may reach the maternal–fetal interface and potentially the developing fetus. However, evidence demonstrating prenatal or fetal exposure is fundamentally different from evidence showing that such exposure is associated with congenital structural anomalies. The extent to which human research has progressed from documenting fetal exposure to evaluating congenital structural anomalies therefore remains unclear. The primary objective of this review is to identify and characterise peer-reviewed human evidence concerning prenatal microplastic exposure and congenital structural anomalies. Secondary objectives are to identify the types of structural anomalies reported; describe the biological matrices and analytical methods used to assess microplastic exposure; characterise microplastic properties such as particle size, abundance, morphology, and polymer composition; map evidence demonstrating maternal–fetal transfer or direct fetal exposure; determine whether comparative, dose–response, or adjusted epidemiological associations have been evaluated; and identify methodological limitations and major evidence gaps. The review will use the **Population–Concept–Context (PCC)** framework and will be conducted in accordance with **Joanna Briggs Institute (JBI) methodological guidance for scoping reviews**. The completed review will be reported according to the **PRISMA Extension for Scoping Reviews (PRISMA-ScR)**. Only **peer-reviewed, full-text primary human studies** will be eligible. Animal studies, in-vitro studies, nanoplastic-only studies, studies in which microplastic-specific findings cannot be separated from combined microplastic–nanoplastic findings, reviews, protocols, preprints, conference abstracts, theses, dissertations, reports, and other grey literature will be excluded. The evidence will be classified into two predefined strata. **Tier 1** will comprise direct congenital-anomaly evidence, including analytical studies evaluating associations between prenatal microplastic exposure and congenital structural anomalies and descriptive studies documenting microplastics among affected pregnancies or fetuses. **Tier 2** will comprise supporting human evidence demonstrating microplastic presence in biologically relevant prenatal or fetal compartments, including the placenta, amniotic fluid, umbilical cord blood, fetal tissues or organs, and meconium reflecting intrauterine exposure. Tier 2 evidence will be used to characterise prenatal/fetal exposure and biological plausibility and will not be interpreted as evidence that microplastics cause congenital anomalies. The review will search **PubMed, Embase, Scopus, Web of Science Core Collection, and CINAHL** from inception to the date of the final search. Embase will be searched through **Embase.com**, and CINAHL through **EBSCOhost**. Backward and forward citation searching will supplement the database searches. Study selection will be conducted independently by two reviewers, with disagreements resolved by consensus or third-reviewer adjudication where necessary. Data will be systematically charted to describe study characteristics, congenital-anomaly phenotypes, biological matrices, microplastic sampling and analytical methods, contamination-control procedures, particle characteristics, polymer composition, exposure–outcome analyses, and other methodological features. No meta-analysis is planned. Findings will instead be synthesised using descriptive numerical summaries, structured evidence tables, narrative synthesis, and graphical evidence mapping where appropriate. The expected outcome is a comprehensive map of the current peer-reviewed human evidence showing how far research has progressed along the pathway from demonstrated prenatal/fetal microplastic exposure to evidence concerning congenital structural anomalies. The review is expected to identify areas where evidence exists, distinguish exposure and co-occurrence evidence from analytical association evidence, identify important methodological and knowledge gaps, and establish priorities for future epidemiological research. It will also help determine whether the human evidence base has become sufficiently developed to justify a subsequent focused systematic review and meta-analysis of associations between prenatal microplastic exposure and congenital structural anomalies.