Background: During IVF treatment, a pharmacological dose of recombinant FSH (rFSH) is used to induce multi-follicular growth (controlled ovarian stimulation; COS). An insufficient dose of rFSH negatively impacts the number of oocytes retrieved, whereas an excessive dose risks the potentially life-threatening complication ovarian hyperstimulation syndrome. Hence, appropriate rFSH dosing is regarded as a key treatment decision affecting both the success and safety of IVF treatment. Current dosing calculators for rFSH are derived to the number of oocytes retrieved, however we hypothesised that rFSH dosing can more accurately be related to follicular growth.
Methods: A single centre retrospective cohort study of 1,034 cycles (January 2012-January 2016) at Hammersmith IVF unit, where rFSH (GonalF) alone was used to induce follicular growth. Follicle sizes at each ultrasound scan and rFSH doses during COS were collated. Relevant univariate and multivariate analyses were conducted.
Results: Recombinant FSH dose adjusted for weight (iU/kg) most accurately predicted serum FSH level (r2=0.352, P<0.0001) suggesting that rFSH dose should be weight-adjusted. Weight-adjusted rFSH dose predicted median follicle size after 5 days and the proportion of antral follicles recruited. Day 5 follicle size predicted follicle size on subsequent scans and thus time to oocyte maturation trigger. No additional improvement in ovarian response was identified at doses beyond 2.25 units/kg. A multivariate model incorporating age, AFC and pre-treatment serum FSH predicted the proportion of antral follicles recruited (r2=0.22, P<0.0001). An insufficient rFSH starting dose necessitating subsequent dose-increase resulted in increased variability of follicle size on day of trigger, negatively impacting the number of mature oocytes retrieved by a median of 5 between high and low dosing groups (P<0.0001).
Conclusion: Recombinant FSH dose should be weight-adjusted. Commencing COS with a sufficient starting dose of rFSH is advantageous, reducing variability in follicle size and improving the number of mature oocytes retrieved.
19 Nov 2018 - 21 Nov 2018