Perinatal outcomes of twin pregnancies discordant for major fetal anomalies

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.

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.

Mean gestational age at delivery, birth weight and perinatal survival rate of twins with and without anomaly.

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.

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.