FSH administration at 12-hour intervals for the first 2 days, combined with mandatory GnRH-agonist trigger and blastocyst vitrification in women (<80Kg) with high AMH levels, results in higher cumulative live birth rates and is safer.

We aimed to determine if a programme change to 12 hourly injections of FSH (150 IU per injection) for the first 2 days of stimulation in women with high ovarian reserve (AMH ≥ 30 pmol/L), followed by 24 hourly injections, would elicit increased earlier follicular recruitment, higher egg yields and blastocyst embryos for cryopreservation, leading to potential higher cumulative pregnancy rates, than conventional daily injections throughout. For safety reasons, the approach required mandatory cryopreservation of all blastocysts (mFET group;  = 74), after ovulation trigger with GnRH-agonist, in GnRH-antagonist controlled cycles. The 'Comparator group' ( = 91) comprised women with the same high AMH levels treated with the same base dose of FSH, with the aim of fresh blastocyst transfer and cryopreservation of supernumerary embryos, treated over the preceding 2 years. There was no difference in age, AMH, weight or BMI between the groups. The mFET group achieved higher egg (17.7 versus 11.7 < 0.001) and embryo (10.9 versus 7.2;  < 0.001) yields and fewer cases with sub-optimal embryo yields (7% versus 22%;  = 0.018). The cumulative live birth rate was superior in the mFET group (73% versus 43%), as was the safety profile, and negligible rate of treatment plan modification.