Objective: To understand the clinical outcomes of frozen embryo transfer and fresh embryo transfer.
Methods: A retrospective analysis was conducted on the clinical data of 870 cases receiving embryo transfer at the Reproductive Medical Center of Sun Yat-Sen Memorial Hospital from January 2013 to March 2014, including 577 cases of in vitro fertilization and fresh embryo transfer, 118 cases of intracytoplasmic sperm injection and fresh embryo transfer and 175 cases of frozen thawed embryo transfer, to compare the clinical characteristics and outcomes between fresh embryo transfer group and frozen embryo transfer group (the patients who had received unsuccessful fresh embryo transfer). The frozen embryo transfer group was divided into pregnant subgroup and non pregnant subgroup to further comparison. Binary logistic regression analyses was performed to identify the influencing factors of pregnancy.
Results: The implantation rate and clinical pregnancy rate were significantly lower in frozen embryo transfer group than in fresh embryo transfer group (26.27% vs. 31.98%, P = 0.01 and 47.43% vs. 65.18%, P < 0.001). The differences in abortion rate, biochemical pregnancy rate and fetal birth weight had no statistical significance between the two groups (P = 0.63, P = 0.17 and P = 0.33). The difference in age between pregnant subgroup and non pregnant subgroup was statistical significant (30.69 ± 3.37 years vs. 32.00 ± 5.09 years, P = 0.03), but no significant differences were found in BMI, duration of infertility and basic endocrine between the two subgroups. Binary logistic regression analysis showed that receiving frozen embryo transfer or not (P < 0.001), wife's age (P < 0.001), BMI (P = 0.011) and number of top quality embryos (P < 0.001) were influencing factors of pregnancy.
Conclusion: Lower implantation rate and clinical pregnancy rate was observed in the patients in frozen embryo transfer group, who had received unsuccessful fresh embryo transfer, but no increase of abortion rate, influence on fetal birth weight and adverse pregnancy outcome were observed.