Objective:To analyze the perinatal risks for the surviving infant of dichorionic twins vanishing twin syndrome (VTS) conceived by assisted reproductive technology (ART).Methods:We used a retrospective cohort study to analyze the clinical data of 4922 frozen-thawed embryo transfer (FET)/fresh embryo transfer cycles in the Department of Reproductive Medicine of the Affiliated Drum Tower Hospital of Nanjing University Medical School from January 2013 to December 2018. This study assessed 4922 cycles (3116 singleton live births from FET cycles and 1806 singleton live births from fresh embryo transfer cycles). The fresh embryo transfer cycles included 1000 singletons following cleavage-stage SET and 806 survivors of VTS following cleavage-stage double embryo transfer (DET). The FET cycles included 2445 singletons (613 cleavage-stage embryo transfer cycles and 1832 blastocyst transfer cycles) following single embryo transfer (SET) and 671 survivors of VTS (385 cleavage-stage embryo transfer cycles and 286 blastocyst transfer cycles) following DET. Baseline characteristics and obstetric outcomes, including gestational age, preterm birth, birth weight, low birth weight, and small-for-gestational-age were analyzed between the two groups.Results:In frozen-thawed blastocyst transfer cycles, VTS group had lower birth weight [(3 316.82±617.69) g vs. (3 405.16±550.68) g, P=0.013] and higher risk of low birth weight [a OR(95% CI)=2.70(1.46-5.00), P=0.002] compared with control group, but no differences of perinatal outcomes were found between VTS and control groups in cleavage-stage tansfer cycles. Conclusion:Surviving infant of dichorionic twins VTS may have higher perinatal risks in blastocyst-stage FET. Selective SET is recommended to obtain singleton pregnancies with a more favorable pregnancy outcome from ART.

Objective:To analyze the perinatal risks for the surviving infant of dichorionic twins vanishing twin syndrome (VTS) conceived by assisted reproductive technology (ART).Methods:We used a retrospective cohort study to analyze the clinical data of 4922 frozen-thawed embryo transfer (FET)/fresh embryo transfer cycles in the Department of Reproductive Medicine of the Affiliated Drum Tower Hospital of Nanjing University Medical School from January 2013 to December 2018. This study assessed 4922 cycles (3116 singleton live births from FET cycles and 1806 singleton live births from fresh embryo transfer cycles). The fresh embryo transfer cycles included 1000 singletons following cleavage-stage SET and 806 survivors of VTS following cleavage-stage double embryo transfer (DET). The FET cycles included 2445 singletons (613 cleavage-stage embryo transfer cycles and 1832 blastocyst transfer cycles) following single embryo transfer (SET) and 671 survivors of VTS (385 cleavage-stage embryo transfer cycles and 286 blastocyst transfer cycles) following DET. Baseline characteristics and obstetric outcomes, including gestational age, preterm birth, birth weight, low birth weight, and small-for-gestational-age were analyzed between the two groups.Results:In frozen-thawed blastocyst transfer cycles, VTS group had lower birth weight [(3 316.82±617.69) g vs. (3 405.16±550.68) g, P=0.013] and higher risk of low birth weight [a OR(95% CI)=2.70(1.46-5.00), P=0.002] compared with control group, but no differences of perinatal outcomes were found between VTS and control groups in cleavage-stage tansfer cycles. Conclusion:Surviving infant of dichorionic twins VTS may have higher perinatal risks in blastocyst-stage FET. Selective SET is recommended to obtain singleton pregnancies with a more favorable pregnancy outcome from ART.