RÉSUMÉ
Objective To compare the perinatal outcomes between singleton and twin pregnancies and the influencing factors in young cases(age < 35)after in vitro fertilization/egg cell sperm injection-embryo transfer (IVF/ICSI-ET). Methods A retrospective study was performed to analysis the perinatal outcomes of the young cases after IVF/ICSI-ET from January 2015 to July 2016.Results The total abortion rate,early abortion rate and the average body weight of the twin group were significantly lower than the singleton group(P < 0.05),the mid-term abortion rate,the preterm delivery rate,cesarean section rate and the low birth weight rate were opposite (P<0.05),while the total pregnancy loss rate and the rate of birth defects were not significantly different between the groups(P>0.05).The frozen-thawed embryo transfer,blastocyst transfer and double-embryo transfer were the risk factors of twin pregnancy. Conclusions Twin pregnancy may increase the risk of adverse perinatal outcomes. Selective single blastocyst transfer during frozen-thawed cycle is an effective measure for young cases,in which it can keep a balance between high clinical pregnancy rate and reducing twin pregnancy rate.