Background: MicroRNAs (miRNAs) are small, non-coding RNA molecules that regulate gene expression and have shown potential as stable, non-invasive biomarkers in peripheral blood. Their expression undergoes dynamic changes during embryo implantation and early pregnancy, making them valuable candidates for predicting reproductive outcomes and identifying complications such as preeclampsia, Recurrent Pregnancy Loss (RPL) and Small-for-Gestational-Age (SGA) births. These insights are particularly relevant for improving Assisted Reproductive Technologies (ART).
Objectives: To systematically evaluate and synthesize current research on the dynamic expression patterns of peripheral blood miRNAs in plasma and assess their potential as non-invasive biomarkers during the preimplantation and pregnancy stages.
Methods: A systematic review and meta-analysis were conducted using ten peer-reviewed studies published between 2020 and 2024. Studies were selected based on their focus on peripheral blood miRNA expression and its relationship with reproductive outcomes. Extracted data included study design, methodologies, patient characteristics, and outcomes such as pregnancy success, embryo transfer efficacy, and complications including preeclampsia, RPL, and SGA births.
Results: The studies applied diverse miRNA detection techniques, including non-invasive culture medium assays, genome-wide expression profiling, and analysis of circulating miRNAs. Differential miRNA expression patterns were linked to specific reproductive outcomes. The findings indicate the predictive value of certain miRNAs in ART success and pregnancy complications.
Conclusion: Peripheral blood miRNAs demonstrate dynamic expression changes during early pregnancy and hold potential as predictive biomarkers for reproductive outcomes. However, methodological variability across studies highlights the need for standardized protocols and further validation in larger, diverse populations.

Keywords:microRNA (miRNA); Peripheral blood biomarkers; Pregnancy biomarkers; Assisted Reproductive Technology (ART)

Abbreviations: miRNA: microRNA; ART: Assisted Reproductive Technology; SGA: Small-for-Gestational- Age; RPL: Recurrent Pregnancy Loss; PE: Preeclampsia; DS: Down Syndrome; CI: Confidence Intervals; SE: Standard Error; ES: Effect Size