Presence of a single fetal major anomaly in a twin pregnancy does not increase the preterm rate

OBJECTIVE: To evaluate whether the presence of one major anomaly in a twin pregnancy would affect the perinatal outcome of the unaffected co-twin. MATERIALS AND METHODS: From 1992 May to July 2003, a total of 1400 twin pregnancies were included in the present study and there were 35 pairs of twins with one major anomaly. Major anomaly was defined as the anomaly that had a significant impact on neonatal morbidity and mortality. The perinatal outcomes of the affected and unaffected co-twins, the gestational age of diagnosis of the anomaly and the gestational age of delivery were the parameters for evaluation. RESULT: The incidence of a twin with one major anomaly was 2.5%. Nineteen of 35 (54.3%) affected twins and five of the 35 (14.3%) unaffected co-twins suffered a perinatal death. In the five cases of unaffected co-twins suffering a perinatal death, four were intrauterine fetal deaths and one was a neonatal death. Three of the perinatal deaths of the unaffected co-twins could be attributed to twin-to-twin transfusion syndrome. The gestational age at delivery, the perinatal mortality rate, and the incidence of low 5 min Apgar scores of the unaffected co-twins were not different from those in twin pregnancies without a major anomaly. CONCLUSION: The perinatal outcomes of the unaffected co-twin were not affected by the fact that its counterpart had one major anomaly, nor were these twin pregnancies at increased risk of preterm labour.