Predictive value of prenatal ultrasound parameters for dichorionic growth discordant twins

Twin growth discordance was demonstrated to be a risk factor for adverse perinatal outcomes, and prenatal ultrasonographic methods were utilized to predict twin growth discordance to improve outcomes. The results currently reported are not consistent due to the poor unified parameters and gestational durations.

A total of 71 dichorionic twins with growth discordance and 346 dichorionic twins with normal growth were respectively included in the retrospective cohort study. The weight discordance of more than 25% was defined as a "growth discordant twin". The clinical baseline information, maternal outcomes, twin birth weights and fetal growth parameters (which were measured by ultrasound) were compared between the two groups from early gestation to late gestation. Multiple logistic regression and receiver operating characteristic curves were adopted to evaluate the predictive value of the growth parameters.

Compared with normal dichorionic twins, the clinical baseline conditions were similar in the twins those finally developed growth discordance. The fetal growth parameters and the deepest volume pocket of amniotic fluid in early and mid-pregnancy showed no obvious predictive values. The fetal growth parameters in late pregnancy showed predictive values, especially the discordance of estimated fetal weight (EFW) in the early third-trimester (P < 0.001, area under the curve, 0.822; the cut-off value, 20%; sensitivity, 66.67%; specificity, 91.30%; positive predictive value, 88.46%).

Two assessment approaches were suggested and adopted to predict twin growth discordance in the current study. Twin growth should be assessed longitudinally and dynamically. Normal twins may show growth imbalance in the early stage. The discordance of EFW in late pregnancy may be a useful indicator for a growth discordance of more than 25%, which is required further confirmation.