[Obstetric and neonatal outcomes of vanishing twin syndrome]

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).

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.

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).

The survivors of vanishing twin syndrome are at a higher risk of having lower birth weight than singletons of single gestation following IVF-ET.