2023, Vol. 27 ›› Issue (24): 3871-3876

Interpretation of the embryo laboratory: number of oocytes retrieved affects the pregnancy outcomes of in vitro fertilization

Gao Wenyi1, Zhang Dong2, Li Caixia1, Du Juan1, Zhang Yanru1, Deng Yun1   

Abstract: BACKGROUND: Controlled ovarian hyperstimulation has gradually become a routine method to increase the number of oocytes retrieved, but there has been controversy over whether the more oocytes retrieved the better. There is still no unified conclusion about the ideal range of egg retrieval number.  
OBJECTIVE: To explore the effect of number of oocytes retrieved on embryo fertilization outcome and clinical pregnancy outcome in fertilization in vitro treatment cycle.
METHODS: 489 patients undergoing in vitro fertilization treatment (including conventional in vitro fertilization and intracytoplasmic sperm injection) were divided into the following five groups according to the number of oocytes retrieved: 1-4 group, 5-8 group, 9-12 group, 13-16 group, and ≥17 group. The fertilization rate, cleavage rate, transferable embryo rate, high-quality embryo rate, and clinical pregnancy outcome were compared in each group, and the effect of the number of oocytes retrieved on the outcome of in vitro fertilization was analyzed.  
RESULTS AND CONCLUSION: The number of oocytes retrieved was significantly correlated with the normal fertilization rate, transferable embryo rate, and high-quality embryo rate. Too many or too few retrieved oocytes could lead to a decrease in the normal fertilization rate and an increase in the abnormal fertilization rate, a decrease in the rates of transferable embryos and high-quality embryos, a decrease in the clinical pregnancy rates, embryo implantation rates, and live birth rates. In conclusion, too many or too few oocytes retrieved can lead to the decline of embryo quality and affect the clinical outcome of in vitro fertilization. The number between 5 and 16 oocytes may be appropriate, while the number between 9 and 12 oocytes may be optimal. During ovulation induction, clinicians should not only aim to increase the number of oocytes retrieved, but should pursue enough high-quality oocytes to reasonably formulate personalized ovulation induction programs for different patients.

Key words: number of oocytes retrieved, fertilization rate, transferable embryo rate, high-quality embryo rate, clinical pregnancy rate, embryo implantation rate, live birth rate