Dynamics of the development of multiple follicles by early versus late hCG administration in ART program.

Objective: To evaluate, in patients stimulated with recombinant FSH and GnRH antagonists, whether triggering the final maturation of oocytes affects IVF outcomes.
Study Design: Five hundred and six IVF procedures were divided into three groups according to the timing of hCG administration: when at least 2 follicles reached the diameter of 17 mm, at least 2 follicles reached 18 mm and at least 2 follicles reached 20 mm. The main outcome was the number of mature oocyte that was the dependent variable of a multivariate model whose independents were, age, AFC, hCG timing, E2 levels at hCG day, number of follicles in different categories of dimension. Secondary endpoints were to compare fertilization, implantation and pregnancy rates in a multilevel multivariate model whose covariates were age, BMI, AFC, embryo quality and cause of infertility.
Results: Timing did not result a statistically significant factor influencing the number of oocytes collected, which was influenced by age, AFC, number of follicles between 12.1 and 15.9 mm and E2 levels. Implantation rate and pregnancy rate appear to be affected only by embryo quality.
Conclusion: The number of oocytes collected and the probability of pregnancy are not associated with the time of hCG administration.