Conventional ovarian stimulation and single embryo transfer for IVF/ICSI. How many oocytes do we need to maximize cumulative live birth rates after utilization of all fresh and frozen embryos?

Abstract STUDY QUESTION What is the impact of ovarian response on cumulative live birth rates (LBR) following utilization of all fresh and frozen embryos in women undergoing their first ovarian stimulation cycle, planned to undergo single embryo transfer (SET). SUMMARY ANSWER Cumulative LBR significantly increases with the number of oocytes retrieved. WHAT IS KNOWN ALREADY Several studies have addressed the issue of the optimal number of oocytes retrieved following controlled ovarian stimulation (COS) for IVF/ICSI and demonstrated that ovarian response is independently related to LBR following IVF/ICSI. The vast majority of studies pertained only to the outcome of the fresh IVF cycle and did not evaluate the cumulative LBR following the transfer of all fresh and frozen–thawed embryos after a single ovarian stimulation, which is the most meaningful outcome for the infertile patient. STUDY DESIGN, SIZE, DURATION This study is a large cohort analysis of retrospective data from January 2009 to December 2013 in a tertiary medical centre, at the Centre for Reproductive Medicine at the University Hospital of Brussels. PARTICIPANTS/MATERIALS, SETTING, METHODS This study included 1099 eligible consecutive women 18–40 years old undergoing their first IVF cycle and planned to undergo SET in their fresh cycle. All patients were treated with a conventional starting gonadotrophin dose of 150–225 IU recombinant FSH (rFSH) in a fixed GnRH antagonist protocol. Vitrification was used as cryopreservation method. To evaluate the impact of oocyte yield on fresh LBR and on cumulative LBR after utilization of all cryopreserved embryos, patients were categorized into four groups according to the number of oocytes retrieved: 1–3 (Group A), 4–9 (Group B), 10–15 (Group C) or >15 oocytes (Group D). MAIN RESULTS AND THE ROLE OF CHANCE Regarding LBR in the fresh IVF/ICSI cycles, unadjusted results did not show any significant difference when comparing either high (>15 oocytes) versus normal (10–15 oocytes) (P = 0.65), or normal (10–15) versus suboptimal (4–9 oocytes) responders (P = 0.2). LBR in the fresh cycles were significantly higher (P < 0.05) in high, normal and suboptimal responders when compared with the low ovarian responder group (1–3 oocytes). Moderate-severe ovarian hyperstimulation syndrome occurred in 11 out of 1099 patients (1%). The cumulative LBR significantly increased with the number of oocytes retrieved (χ2 test for trend P < 0.001). High responders (>15 oocytes) de