[Retrospective analysis of outcomes of selectively or spontaneously reduced multiple pregnancies out of 6 917 in vitro fertilization-embryo transfer pregnancy cycles].

To analyze the effects of fetal reduction in early pregnancy on obstetric and neonatal outcomes of spontaneously or selectively reduced multiple pregnancies produced by in vitro fertilization-embryo transfer (IVF-ET). Retrospective study of 6 917 clinical pregnancies from IVF-ET cycles, including 754 multiple pregnancies divided into two groups according to the remaining fetus number: reduced singleton group (599) and reduced twin group (155); and maternal and neonatal outcomes of two groups were compared to primary singleton group (3 589) and primary twin group (2 574). The rate of pregnancy complication [9.85%(59/599) versus 6.21%(223/3 589)], preterm birth [19.37%(116/599) versus 10.73%(385/3 589)], low birth weight [9.71%(56/577) versus 4.57% (152/3 324)], perinatal death [0.69%(4/577) versus 0.12%(4/3 324)] and malformation [2.95%(17/577) versus 1.02%(34/3 324)] in reduced singleton group were significantly higher than those in primary singleton group (all 0.01). There were no significant differences between reduced twin group and primary twin group (all 0.05). In reduced singleton group, birth defect rate was 2.95%, which was higher than those of the other three groups (0.05), in this group spontaneous pregnancy reduction accounted for 89.3% (535/599). (1) The rate of pregnancy complication, preterm birth, low birth weight, perinatal death and malformation in reduced singleton group are still higher than primary singletons, suggesting embryo reduction only is a compensated method in multiple pregnancies. Limiting the number of embryos transferred is the essential solution. (2) The rate of birth defect in spontaneous pregnancy reduction group is higher, so prenatal examination should be reinforced in this group.