Fetal growth disorders in twin gestations.

PURPOSE OF REVIEW: Twin gestations account for approximately 3% of all births. Although there appear to be physiologic differences in the third trimester growth of twins compared with singleton gestations, reasons for this remain unclear. As growth-restricted fetuses and neonates are at increased risk for adverse outcomes, there is a clinical need to optimize our ability to delineate normally from pathologically grown twins. RECENT FINDINGS: Recent studies have addressed current limitations in the way growth restriction is diagnosed in twin gestations. Twin-specific fetal and neonatal growth charts have been shown to decrease the number of cases inappropriately labeled as growth restricted compared with singleton nomograms. In addition, individual growth assessment (IGA) is a promising method of diagnosing pathological growth using each fetus's growth potential rather than a comparison of the estimated fetal weight with population nomograms. SUMMARY: There is a recent focus on improving our understanding of physiologic and pathologic twin growth. The increased use of twin-specific growth curves is likely to result in a decrease in the incidence of FGR diagnosis among twin gestations and could improve the outcomes of twins currently misclassified as FGR. Future research will hopefully clarify the reasons behind differences seen in twin versus singleton third trimester twin growth.