Abstract: Objective To compare the obstetric and neonatal outcomes of singleton pregnancies originating from vanishing twin
syndrome with those of singleton pregnancies originating from a single gestation following in vitro fertilization-embryo
transfer (IVF-ET). Methods This case-control study involved a total of 409 singleton deliveries after IVF-ET/freeze-thawed
embryo transfer, including 44 survivors of vanishing twin syndrome (study group) and 365 singletons (control group). The
duration of gestation, rate of preterm delivery, neonatal birth weight and proportion of low birth weight were compared
between the two groups. Results Of all the singletons born, 10.8% originated from a vanishing twin gestation. No differences
were found in the duration of gestation between the two groups. The mean gestational age was 38.29±1.76 vs 38.45±1.40 weeks
(P=0.495) in the study group and controls group, with the rate of preterm delivery of 15.9% vs 10.13% (P=0.298), respectively.
The mean birth weight was significantly higher in the control group (3261.8 ± 437.85 g vs 3086.8 ± 527.01 g, P<0.05), but the
proportion of low birth weight (<2500 g) showed no significant difference between the study and control groups (6.82% vs
2.74%, P=0.316). Conclusions The survivors of vanishing twin syndrome are at a higher risk of having lower birth weight than
singletons of single gestation following IVF-ET.