[Frozen-thawed embryo transfer (FET) versus fresh embryo transfer in clinical pregnancy rate during in vitro fertilization-embryo transfer].

Objective: To investigate whether frozen-thawed embryo transfer (FET) instead of fresh embryo transfer for the first embryo transfer (ET) in a controlled ovarian hyperstimulation (COH) cycle improves the in vitro fertilization-ET clinical pregnancy rate.

Methods: The investigators retrospectively analyzed the clinical data of 1341 IVF-ET cycles under COH, including 1169 fresh ET cycles (Group T1) and 172 FET cycles as the first embryo transfer in COH cycle (Group C1). Logistic regression was used to model the probability of clinical pregnancy rate based on age, ET method and other cycle-specific factors.

Results: The clinical pregnancy rate was significantly higher in Group C1 than in Group T1 (63.4% vs 49.4%, P < 0.01). Multivariate logistic regression analysis revealed significant associations between the number of high-quality embryos transferred, patient age and ET method in clinical pregnancy rate. After adjusting for the number of high-quality embryos transferred and age, the clinical pregnancy rate remained significantly higher in Group C1 than in Group T1 (odds ratio: 1.75, 95% confidence interval: 1.25 - 2.46; P < 0.01). Significant differences were found in age (< 35 years old) and the number of retrieved oocytes (> or = 15).

Conclusion: Using FET instead of fresh embryo transfer can improve the clinical pregnancy rate and the efficiency of IVF-ET.