Objective: To investigate the spontaneous pregnancy reduction (SPR) rate, SPR-related factors and the effects of SPR on pregnancy outcomes in the patients with multiple pregnancies undergoing in vitro fertilization/intracytoplasmic sperm injection-embryo transfer (IVF/ICSI-ET).
Methods: Between January 1998 and December 2010, 3957 patients undergoing fresh/frozen-thawed cycles (IVF/ICSI-ET) and their 5106 neonates were enrolled in this study. According to spontaneous pregnancy reduction (SPR), this study included singleton originating from twins [(2→1) group] or from triplets [(3→1) group], and twins originating from triplets [(3→2) group]. According to SPR time, this study included ≤8 week, 8-18 week and ≥18 week's groups. Outcome measures were SPR rate, preterm rate, mean birth weight and the rates of low birth weight and very low birth weight.
Results: SPR rate was higher in triplets group than in twins group, in frozen-thawed cycles than in fresh cycles, in the patients ≥35 years than in the patients <35 years (all P<0.05). Compared with ≤8 week group, preterm rate was significantly increased in 8-18 week group (P<0.05). Pregnancy outcomes were better in (2→1) group than in twins group, in (3→1) group than in triplets group (all P<0.05). After multi-fetal pregnancy reduction (MFPR), the mean birth weight was higher and low birth weight was lower in SPR group than in only MFPR group (all P<0.05).
Conclusion: SPR rate is related to age and the initial number of gestational sacs. Both SPR and MFPR can improve pregnancy outcomes. The later the SPR occurs, the worse the neonatal outcomes are. Due to the possibility of SPR, it is necessary to appropriately delay MFPR until 8 gestational weeks.
Keywords: In vitro fertilization; embryo transfer; intracytoplasmic sperm injection; multiple pregnancy; pregnancy outcomes; spontaneous pregnancy reduction.