A high number of oocytes obtained after ovarian hyperstimulation for in vitro fertilization or intracytoplasmic sperm injection is not associated with decreased pregnancy outcome

Abstract

To investigate the possible negative effects of a strong ovarian response on oocyte quality. Retrospective study. Tertiary academic center. A total of 1,894 women (IVF, n = 1,544; ICSI, n = 350) who underwent their first ovarian stimulation cycle during the period 1995-2002. Standardized controlled ovarian stimulation with urinary FSH or recombinant FSH after pituitary down-regulation, followed by IVF/intracytoplasmic sperm injection (ICSI) and ET. Fertilization rate, fraction of high-quality embryos, and implantation rate. Using multivariate logistic regression, we analyzed the effect, expressed as an odds ratio (OR), of the number of oocytes obtained (i.e., ovarian response) on the outcome measures. No effect of the response on the ongoing implantation rate or fraction of high-quality embryos was observed. Both in IVF (OR = 0.81, 95% confidence interval [CI] 0.75-0.87) and in ICSI (OR = 0.88, 95% CI 0.76-1.00), a negative effect of increasing ovarian response was seen on the fertilization rate per oocyte obtained. However, no negative effect was observed on the fertilization rate per oocyte injected in ICSI (OR = 1.00, 95% CI 0.87-1.14). The fraction of immature oocytes rises from 3.9%, in women with < or = 3 oocytes, to 26% in women with > 20 oocytes. Oocytes from high responders contain a greater fraction of immature oocytes, but pregnancy outcome is not impaired.