Risk factors associated with stillbirth and adverse perinatal outcomes in dichorionic twin pregnancies complicated by selective fetal growth restriction: a cohort study.

OBJECTIVE: The main aim of this study was to investigate the perinatal outcomes of dichorionic twin pregnancies complicated by selective fetal growth restriction (sFGR). DESIGN: Retrospective cohort study. SETTING: Tertiary reference centre. POPULATION: Dichorionic twin pregnancies complicated by sFGR between 2000 and 2019 in St George's University Hospital. METHODS: Regression analyses were performed using generalised linear models and mixed-effects generalised linear models where appropriate to account for pregnancy level dependency in variables. Time to event analyses were performed with mixed-effects Cox regression models. MAIN OUTCOME MEASURES: Stillbirth, neonatal death or neonatal unit admission with morbidity in one or both twins. RESULTS: A total of 102 (of 2431 dichorionic twin pregnancies) pregnancies complicated by sFGR were included in the study. The Cochrane-Armitage test revealed a significant trend for increased adverse perinatal outcome rates with more severe forms of umbilical artery flow impedance, i.e. reversed, absent, positive with resistant flow and positive flow without resistance. A multivariable model including maternal and conception characteristics had poor predictive accuracy for stillbirth (area under the curve: 0.68, 95% confidence interval [CI] 0.55-0.81) and composite adverse perinatal outcomes (area under the curve: 0.58, 95% CI 0.47-0.70). When umbilical artery Doppler parameters were added to the models, the area under the curve values improved to 0.95 (95% CI 0.89-0.99) and 0.83 (95% CI 0.73-0.92) for stillbirth and composite adverse perinatal outcomes, respectively. CONCLUSION: In dichorionic twin pregnancies complicated by sFGR, the umbilical artery Z-scores were associated with both intrauterine death and adverse perinatal outcomes.