Background: Fresh embryo transfer has been decreasing because of advancements in vitrification techniques and safety concerns related to ovarian hyperresponse. However, in normal responders, clinical outcomes appear to be comparable with those with frozen embryo transfer. This study aimed to determine factors that influence successful fresh embryo transfer.
Methods: This retrospective cohort study included 521 women who underwent in vitro fertilization (IVF) and fresh embryo transfer at King Chulalongkorn Memorial Hospital, Thailand. Patients’ clinical data, embryo details, endometrial characteristics (thickness and pattern), and embryo transfer procedures (tip and flow during transfer, embryo placement location, difficulty of the procedure, and presence of blood and mucous at catheter) were analyzed. Chi-square test, Fisher’s exact test, Student’s t-test, and logistic regression were performed for data analysis. A p-value of <0.05 was considered statistically significant.
Results: The overall clinical pregnancy rate was 17.1%. Women aged >40 years were less likely to have a clinical pregnancy than those aged <35 years (adjusted odds ratio [aOR] 0.422; 95% confidence intervals [CI] 0.196-0.908, p=0.027). Day 3 embryo transfer showed a significant decrease in clinical pregnancy compared with blastocyst transfer (aOR 0.514; 95%CI 0.287-0.923, p=0.026). In the subgroup analysis for blastocyst transfer, women with good-quality blastocyst (≥322) were 2.439 times more likely to have a clinical pregnancy than those with poor-quality blastocysts (aOR 2.439; 95%CI 1.199-4.962, p=0.014).
Conclusion: Advanced age and day 3 embryo transfer were significantly associated with low clinical pregnancy rates in fresh embryo transfer.