Oocyte number per livebirth in IVF: were Steptoe and Edwards less wasteful?

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Objective: A historical comparison between the number of oocytes required for livebirth in IVF at Bourn Hall Clinic in 1980–1983 and in 2000. Design: Retrospective analysis. Materials and Methods: A series of 847 consecutive long down regulation GnRHa IVF cycles carried out at Bourn Hall Clinic (BHC) between January–December 2000 was reviewed. For the purpose of data analysis, nine cycles in which there was complete failure of fertilization, and 30 cycles in which all embryos were frozen due to risk of OHSS were excluded from the study; the outcome of 808 cycles resulting in fresh embryo transfer was confirmed by follow-up. Standard long down-regulation was accomplished with luteal phase intranasal Nafarelin, 400 micrograms twice daily. After confirmation of downregulation, recombinant-hFSH (Gonal-F(r), Serono) was administered at a starting dose based on age, previous IVF response, weight and baseline laboratory results. The mean patient age was 33.5, with a range of 21–47. Generally, patients aged <35 years started with 150 IU, those aged 35–39 years with 225 IU and aged 40 years or older started with 300 IU or more. HCG was administered when two or more follicles were at least 18 mm (but preferably less than 22 mm) in diameter, coinciding with at least 7mm endometrial thickness and estradiol preferably between 70 pg/ml–140 pg/ml per large follicle. HCG dosage of 10,000 IU was used unless OHSS risk justified 5,000 IU. Luteal phase support was started on the day of oocyte retrieval, in the form of vaginal or rectal Cyclogest(r) (Cox Pharmaceuticals, UK) 400 mg twice daily or Crinone(r) (Serono) 8% vaginally once daily. Two embryos (occasionally 3 in selected cases) were transferred on day 2 or 3 using the Edwards-Wallace soft embryo transfer catheter.The data was tabulated according to age and number of oocytes retrieved. Low Yield (LY) patients were defined as those in whom 1–5 oocytes retrieved, Intermediate Yield (IY) patients had 6–15 oocytes retrieved and High Yield (HY) patients had 16 or more oocytes retrieved. Results: Patients were subdivided into groups by age (< 37 yrs, 38+ yrs), and by oocyte yield (low, intermediate, high). In patients less than 38 years of age, fertilization rates and livebirth deliveries were equivalent, irrespective of the number of oocytes retrieved. Those who yielded Low numbers of oocytes (1–5) required 9.6 oocytes per livebirth, compared with 25.1 and 51.5 in those who yielded Intermediate (6–16) and High (16+) numbers of oocytes. Conclusion: Although we now have more than 20 year’s experience of superovulation for IVF treatment, our results suggest that the efficiency of oocyte utilization has not significantly improved since the early 1980’s. We raise the question of whether milder stimulation regimes will produce the oocyte destined for a livebirth: does collecting fewer oocytes provide a better clinical strategy for oocyte selection than does the harvesting of large numbers of oocytes?