Obstetrical and Neonatal Outcomes in Twin Pregnancies Based on Chorionicity: A Systematic Review of ART-Conceived Monochorionic vs. Dichorionic Twins

Background: Assisted reproductive technology (ART) is increasingly utilized worldwide, and approximately 30% of ART pregnancies result in twin gestations. Chorionicity strongly influences perinatal risk, yet its specific impact on ART-conceived twins has not been systematically clarified. Objective: To compare obstetrical and neonatal outcomes in assisted ART-conceived monochorionic (MC) versus dichorionic (DC) twin pregnancies and evaluate the impact of chorionicity on maternal and perinatal outcomes. Methods: This systematic review was conducted according to PRISMA guidelines and registered in PROSPERO (CRD42024600292). PubMed, Scopus, and Web of Science were searched through October 2024 for studies comparing obstetrical and neonatal outcomes in ART-conceived monochorionic and dichorionic twin pregnancies. Eligible studies were qualitatively synthesized. Results: Thirty-five studies comprising 15,648 ART-conceived twin pregnancies were included, including 371 monochorionic and 15,277 dichorionic pregnancies. MC pregnancies consistently demonstrated less favorable perinatal outcomes compared with DC pregnancies, including an earlier gestational age at delivery, increased prematurity, lower birth weight, and higher rates of perinatal mortality. By contrast, maternal complications, such as hypertensive disorders, gestational diabetes mellitus, PROM, and cesarean delivery, varied considerably across the studies without a consistent association with chorionicity. The baseline maternal characteristics were generally comparable between the groups. Conclusions: Monochorionicity in ART-conceived twin pregnancies is associated with increased adverse neonatal and perinatal outcomes, particularly prematurity and perinatal mortality, while maternal outcomes appear less clearly influenced by chorionicity. Standardized prospective studies are needed to further clarify the chorionicity-specific risks in ART twin pregnancies.