Perinatal outcomes of twin pregnancies discordant for major fetal anomalies

OBJECTIVE: The aim of this study was to determine perinatal outcomes of twin pregnancies discordant for a major fetal anomaly and to compare with twins without anomaly. METHODS: All twin pregnancies admitted or referred to the maternal-fetal unit were prospectively entered into a computer database. Chorionicity, fetal anomaly, mean gestational age at delivery, birth weight and perinatal survival rate were reviewed. MAIN OUTCOME MEASURES: Mean gestational age at delivery, birth weight and perinatal survival rate of twins with and without anomaly. RESULTS: There were 48 cases of monochorionic diamniotic (MCDA), 2 cases of monochorionic monoamniotic (MCMA) and 217 twins with dichorionic (DC) placentation. Out of 267 twin pregnancies, there were 17 (6.3%) twins with fetal anomaly. Twins discordant for a major fetal anomaly were diagnosed in 13 cases (4.8%). We observed 3 cases with MCDA and 10 cases with DC placentation and the incidence of discordance for a major fetal anomaly as 4.6% (10/217) in DC and 6.0% (3/50) in MC twin pregnancies. We identified 8 cases (62%) with craniospinal, 2 (15%) with gastrointestinal, 2 (15%) with urinary system, and 1 case (8%) with both craniospinal and gastrointestinal anomalies. There were significant differences between the normal co-twin of the major anomaly group (n = 13) and twins without anomaly group (n = 235) in mean gestational age at delivery (32 vs. 34 weeks; p = 0.029), mean birth weight (1,640 vs. 2,030 g; p = 0.022) and perinatal survival rate (69.2 vs. 91.1%; p = 0.018), respectively. CONCLUSION: The presence of a fetus with a major anomaly in a twin gestation increases the risk of preterm delivery, low birth weight and perinatal mortality of the normal co-twin.