To determine the optimal antenatal surveillance strategy and timing of delivery for monoamniotic twin pregnancies. Obstetric and perinatal outcomes were retrospectively retrieved for 115 monoamniotic twin pregnancies managed in 5 referral units in the last decade. Women were either offered the option of intensive fetal surveillance as inpatients starting prior to 29 weeks gestation, or outpatient follow-up. Caesarean section was performed between 32-34 weeks in otherwise uncomplicated pregnancies. Fetal anomalies were present in 12.2% (n=28). Four selective reductions were performed. There were 41 spontaneous fetal demises (17.8%). Six pregnancies were terminated. Neonatal survival was 71% (n=163/230). The prospective risk of intra-uterine fetal death reached a nadir at 2.4% at 28 weeks gestation. The prospective risk of a severe neonatal complication (defined as a composite outcome of death, intraventricular hemorrhage>grI, periventricular leucomalacia, retinopathy of prematurity, sepsis or necrotizing enterocolitis) was lower than the prospective risk of intra-uterine fetal demise after 32+4 weeks gestation. Of 84 pregnancies with 2 fetuses alive at 28 weeks gestation, 67 were uncomplicated. 37 were admitted for fetal surveillance and 30 were managed as outpatients. Delivery for fetal distress was similar in electively admitted inpatients and in outpatients (30 vs. 27%;p=1.0), yet gestational age at delivery was 8 days later in outpatients (32.1±1.4 vs 33.2±1.8wks). In each group, 1 double intra-uterine fetal death occurred after 33 weeks. Postnatal ventilation was shorter in fetuses managed as outpatients (2 days vs 4 days in inpatients), but the risk of neonatal death (n=1 in each group) or other neonatal complications was similar. Optimal timing of delivery of uncomplicated monoamniotic twin pregnancies is 32+4 weeks gestation. Outcomes appear similar in pregnancies managed in an inpatient or outpatient setting. Data are being collected in 3 other centers and will be presented at the meeting.