Original Article . . . . . . . . . . . . . . Perinatal Outcome of Vaginally Delivered Twin Gestations With a Larger Twin B Ihab M. Usta, MD Anwar H. Nassar, MD Antoine A. Abu Musa, MD Johnny T. Awwad, MD Khalid A. Yunis, MD Muhieddine A.-F. Seoud, MD OBJECTIVE: To study the perinatal outcome of vaginally delivered twins when twin B is more than 250 g larger than twin A. STUDY DESIGN: Maternal and neonatal charts of live-born, nonanomalous twins, >25 weeks’ gestation and vaginally delivered over a period of 17 years were reviewed. The results of this review were distributed among two groups: (1) those with twin B more than 250 g larger than twin A (DBW>250) and (2) those where the difference was <250 g (DBW<250). For vaginally delivered twin gestations, the perinatal outcome of twin B in the group DBW>250 was compared to that of its co-twin, and to that of twin B in the group DBW<250. RESULTS: Of the 679 twin gestations reviewed, 138 (20.6%) were in the group DBW>250, of whom 73 (52.9%) delivered vaginally despite malpresentation in 39.7%. The vaginally delivered twin pregnancies in the groups DBW>250 (n ¼ 73) and DBW<250 (n ¼ 303) had similar demographics, parity, presentation, gestational age at delivery, and duration of the first stage of labor. Discordant twins were more frequent in the group DBW>250 (26.0 versus 9.5%, p ¼ 0.001). Twin B in the group DBW<250 was smaller, with higher incidence of growth restriction, low 5 min Apgar score, and hyperbilirubinemia compared to twin B in the group DBW>250. There was no difference in the incidence of intraventricular hemorrhage, seizures, sepsis, neonatal death, and median nursery stay. Except for a lower median Apgar score at 1 min in twin B and a longer median nursery stay in twin A, twins A and B in the group DBW>250 were similar regarding all other neonatal outcome variables. CONCLUSIONS: When twin B is more than 250 g larger than A, and both are delivered vaginally, the perinatal outcome is similar to its co-twin as well as to that of twin B of all other vaginally delivered twins. That twin B is larger than A is not itself a contraindication to attempted vaginal delivery. Journal of Perinatology (2003) 23, 409–413. doi:10.1038/sj.jp.7210935 INTRODUCTION A substantially larger second twin occurs infrequently in twin pregnancies. 1–3 With the incorporation of ultrasound to estimate fetal weight, 4 obstetricians may be reluctant to allow vaginal delivery when twin B is substantially larger than twin A, more so when twin B is in an abnormal presentation. 5 Few studies in the literature address the dilemma of management and outcome of vaginally delivered twin gestations where B is more than 250 g larger than A. The purpose of our study was to compare the perinatal outcome of twin B in such cases to that of its co-twin, and to that of twin B in all other vaginally delivered twin pregnancies. MATERIALS AND METHODS After IRB approval, twin gestations delivered between 1984 and 2000 inclusive were identified from our labor and delivery database. Only nonanomalous, live on admission, >25 weeks twin gestations were included. Cases of twin–twin transfusion syndrome defined as a discharge diagnosis of twin–twin transfusion syndrome, >20% birthweight discordance, ultrasound-determined oligohydramnios in one and polyhydramnios in the other, and a monochorionic placenta (gross or pathologic examination) were excluded. Maternal charts were reviewed by two authors (IU or AN) for maternal and gestational age, presentation, parity, mode of delivery, duration of the stages of labor, oxytocin use, and traumatic delivery. Neonatal charts were reviewed by three authors (IU, AN, or KY) for birth weight, gender, Apgar scores, growth restriction, suspected as well as proven sepsis, hyperbilirubinemia, transfusion, intraventricular hemorrhage, respiratory distress Address correspondence and reprint requests to Ihab M. Usta, MD, Department of Obstetrics and Gynecology, American University of Beirut-Medical Center, PO Box 113-6044/C53, Beirut, Lebanon. Department of Obstetrics and Gynecology (I.M.U., A.H.N., A.A.A.M., J.T.A., M.A.-F.S.), American University of Beirut Medical Center, Beirut, Lebanon; and Department of Pediatrics (K.A.Y.), American University of Beirut Medical Center, Beirut, Lebanon. Journal of Perinatology 2003; 23:409–413 r 2003 Nature Publishing Group All rights reserved. 0743-8346/03 $25 www.nature.com/jp 409