RESUMO
RESEARCH QUESTION: In patients with 1-3 embryos available on day 3, does blastocyst transfer reduce the chances of a clinical pregnancy by cancelling transfer cycles compared with cleavage transfer? DESIGN: This retrospective observational study included 423 IVF cycles performed from 1 January 2019 to 31 December 2020 at the Center for Reproduction and Fertility of the Second Affiliated Hospital of Kunming Medical University. Cleavage transfer was performed in 267 cycles and blastocyst transfer was performed in 156 cycles. The primary outcome was the ongoing pregnancy rate, and the secondary outcomes were clinical pregnancy rate and embryo cessation rate. Univariate analysis was performed to compare outcomes. A logistic regression analysis was performed to explore the association between transfer stage and ongoing pregnancy rate. RESULTS: No differences were observed in the ongoing pregnancy rate (25.84% versus 26.92%; odds ratio [OR] 0.95; 95% confidence interval [CI] 0.61-1.50; P = 0.82) and embryo cessation rate (83.48% versus 85.75%; OR 1.19; 95% CI 0.82-1.75; P = 0.40) between the two groups. Logistic regression analysis showed no association between transfer stage and ongoing pregnancy rate (OR 1.06; 95% CI 0.64-1.73). CONCLUSIONS: Blastocyst transfer does not reduce the chances of a clinical pregnancy. These results support the proposal of blastocyst transfer in patients with 1-3 embryos available on day 3.