Intrapartum Fetal Compromise in Late-Onset Fetal Growth Restriction Using the Modified Myocardial Performance Index: A Prospective Cohort Study.

Background and Objectives: Predictive performance of the modified myocardial performance index (Mod-MPI) for emergency cesarean delivery secondary to intrapartum fetal compromise (IFC) was examined in late-onset fetal growth restriction (FGR) or small-for-gestational-age (SGA) pregnancies. Materials and Methods: This prospective observational cohort comprised 120 singleton term pregnancies affected by late-onset FGR or SGA, classified in line with the Delphi consensus criteria, for whom a trial of vaginal delivery was planned. The primary endpoint was emergency cesarean delivery indicated by IFC, while the secondary endpoint was the development of composite adverse perinatal outcomes (CAPO). Measurements of Mod-MPI, the umbilical artery, the middle cerebral artery, and the cerebroplacental ratio (CPR) were performed within the final 72 h before delivery and were blinded to the clinicians managing the intrapartum period. Results: IFC constituted 28.3% (n = 34) of the study cohort. The IFC group exhibited significantly higher Mod-MPI values and lower CPR values (p < 0.001). In multivariable analysis, elevated Mod-MPI (≥0.61) and reduced CPR (<5th percentile) were identified as independent predictors of IFC. On receiver operating characteristic analysis, Mod-MPI demonstrated superior discriminative performance compared with CPR for predicting IFC (area under the curve [AUC]: 0.835 vs. 0.759). In contrast, CPR showed the highest diagnostic performance for predicting CAPO (AUC: 0.779). Conclusions: Mod-MPI reflects subclinical cardiac dysfunction in fetuses with late-onset FGR and SGA and represents a valuable parameter for predicting tolerance to acute intrapartum stress. Rather than routine implementation, it appears most appropriate as a complementary tool contributing to intrapartum risk assessment in selected high-risk cases.