Fetal growth disorders in twin gestations

Abstract

Purpose of reviewTwin 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 findingsRecent 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.SummaryThere 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.

Twin charts should be the standard reference to assess growth in twin pregnancy

“…However, there is a growing body of evidence that twin-specific standards are well tolerated, have similar ability to identify foetuses at risk of stillbirth and are less likely to classify foetuses as growth-restricted, therefore, reducing the frequency of additional scans, hospital visits and maternal stress (Fig. 1) [61]. This also translates into lower rates of unnecessary antenatal steroid administration, iatrogenic preterm deliveries and neonatal unit admissions.…”

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“…The idea that twin-specific growth curves reduce the number of twins incorrectly classified as growth restricted was recently addressed by researchers from California and New York (Blumenfeld & Anderson, 2023). They begin by defining small-for-gestational age (SGA) and fetal growth restriction (FGR), terms that have been used interchangeably and, as such, inappropriately.…”