Analysis of factors related to early miscarriage after in vitro fertilization embryo transfer

Aims

This research aims to explore the factors related to early spontaneous miscarriage after in vitro fertilization and embryo transfer (IVF-ET) pregnancy, and to provide guidance for improving pregnancy outcomes.

Methods

We retrospectively analyzed the data for clinical pregnant women (2591 cycles) undergoing IVF-ET at the reproductive center of Peking University People’s Hospital from January 2017 to December 2018; This included 544 ​ET cycles and 2047 frozen embryo transfer cycles. The analysis of factors associated with early miscarriage in the overall population of IVF/intracytoplasmic sperm injection (ICSI) pregnancies (including fresh and thawing cycles) was performed.

Results

The risk of early miscarriage in the 35–39 age group was 1.35 times higher than that in the <35 age group (OR ​= ​1.35 [1.05,1.73], p ​= ​0.02). In addition, the risk of early miscarriage was 3.88 times higher in the group ≥40 years old than in the group <35 years old (OR ​= ​3.88 [2.68,5.62], p ​< ​0.001). Endometrial thickness also affected the miscarriage rate; the early miscarriage risk with endometrial thickness ≥8.5 ​mm was 0.78 times than that of the <8.5 ​mm group (OR ​= ​0.78 [0.62,0.98], p ​= ​0.03). The early miscarriage rate during frozen embryo transfer was 1.48 times higher than that during fresh embryo transfer (OR ​= ​1.48 [1.08,2.02], p ​= ​0.01), while in the fresh cycle, the risk of early miscarriage with high-quality embryos was 0.5 times lower than that with non-high quality embryos (OR ​= ​0.5 [0.27,0.9], p ​= ​0.02). In the frozen cycle, the risk of early miscarriage in natural cycle transplantation was 0.73 times that in hormone replacement treatment (HRT) cycle transplantation (OR ​= ​0.73 [0.54,0.97], p ​= ​0.03) .

Conclusions

Advanced age is an independent risk factor for early miscarriage, while endometrial thickness at the date of transplantation is an independent protective factor. The risk of early miscarriage in fresh-cycle transplanted embryos is significantly lower than that in frozen embryos, and the number of high-quality embryos in the fresh cycle lowers the miscarriage rate significantly. Natural cycle transplantation has a lower rate of early miscarriage than hormone replacement therapy.