Comparison of blastocyst euploidy rates following luteal versus follicular phase stimulation in a GnRH antagonist protocol: a prospective study with repeated ovarian stimulation cycles.

STUDY QUESTION

Is there any difference in the mean number of euploid embryos following luteal phase start (LS) and follicular phase start (FS) of ovarian stimulation?

SUMMARY ANSWER

The mean number of euploid blastocysts is equivalent independent of whether the inseminated oocytes are derived from FS or LS.

WHAT IS KNOWN ALREADY

Starting ovarian stimulation at any time of the cycle ('random-start') is commonly used for emergency fertility preservation in cancer patients. A few retrospective studies have been published evaluating LS in women undergoing ovarian stimulation in the context of IVF, but there is a lack of robust data on the comparative efficacy of LS versus FS.Although 'random start' is commonly used in cancer survivors, few retrospective and uncontrolled studies have been published evaluating luteal phase stimulation in women undergoing ovarian stimulation in the context of IVF. Owing to this evident lack of robust data on the efficacy of LS, guidelines typically recommend the LS approach only for medical reasons and not in the context of IVF.

STUDY DESIGN, SIZE, DURATION: This is a prospective, equivalence study, with repeated stimulation cycles, conducted between May 2018 and December 2021. Overall, 44 oocyte donors underwent two identical consecutive ovarian stimulation cycles, one initiated in the FS and the other in the LS. The primary outcome of the study was to evaluate whether FS and LS in the same patient would result in equivalent numbers of euploid embryos following fertilization of oocytes with the same sperm sample.

PARTICIPANTS/MATERIALS, SETTING, METHODS: Overall, 44 oocyte donors underwent two consecutive ovarian stimulation protocols with 150 μg corifollitropin alpha followed by 200 IU recombinant FSH (rFSH) in a fixed GnRH antagonist protocol. The only difference between the two cycles was the day of initiation of ovarian stimulation, which was in the early follicular phase (FS) in one cycle, and in the luteal phase (LS) in the other. Forty-four oocyte recipients participated in the study receiving a mean of six metaphase II (MII) oocytes from each stimulation cycle (FS and LS). All MIIs were inseminated with the corresponding recipient's partner sperm (which had been previously frozen) or donor sperm, in order to safeguard the use of the same sample for either the FS or LS. Following fertilization and blastocyst culture, all generated embryos underwent genetic analysis for aneuploidy screening (preimplantation genetic testing for aneuploidy).

MAIN RESULTS AND THE ROLE OF CHANCE

FS resulted in a significantly shorter duration of ovarian stimulation (difference between means (DBM) -1.05 (95% CI -1.89; -0.20)) and a lower total additional dose of daily rFSH was needed (DBM -196.02 (95% CI -319.92; -72.12)) compared with LS. The donors' hormonal profile on the day of trigger was comparable between the two stimulation cycles, as well as the mean number of oocytes (23.70 ± 10.79 versus 23.70 ± 8.81) (DBM 0.00 (95% CI -3.03; 3.03)) and MII oocytes (20.27 ± 9.60 versus 20.73 ± 8.65) (DBM -0.45 (95% CI -2.82; 1.91)) between FS and LS cycles, respectively. Following fertilization, the overall blastocyst formation rate was 60.70% with a euploid rate of 57.1%. Comparisons between the two stimulation cycles did not reveal any significance differences in terms of fertilization rates (71.9% versus 71.4%), blastocyst formation rates (59.4% versus 62%) and embryo euploidy rates (56.9 versus 57.3%) for the comparison of FS versus LS, respectively. The mean number of euploid blastocysts was equivalent between the FS (1.59 ± 1.30) and the LS (1.61 ± 1.17), (DBM -0.02 (90%CI -0.48; 0.44)).

LIMITATIONS, REASONS FOR CAUTION: The study was performed in young, potentially fertile oocyte donors who are patients with high blastocyst euploidy rates. Although results may be extrapolated to young infertile women with good ovarian reserve, caution is needed prior to generalizing the results to infertile women of older age.

WIDER IMPLICATIONS OF THE FINDINGS

The current study provides evidence that initiation of ovarian stimulation in the luteal phase in young potentially fertile women may result in a comparable number of oocytes and comparable blastocyst euploidy rates compared with follicular phase stimulation. This may imply that in case of a freeze-all protocol in young patients with good ovarian reserve, clinicians may safely consider initiation of ovarian stimulation during the luteal phase.

STUDY FUNDING/COMPETING INTEREST(S): This research was supported by an unrestricted grant from MSD/Organon. N.P.P. has received Research grants and honoraria for lectures from: Merck Serono, MSD/Organon, Ferring Pharmaceuticals, Besins Intenational, Roche Diagnostics, IBSA, Theramex, Gedeon Richter. F.M., E.C., M.R. and S.G. declared no conflict of interests.

TRIAL REGISTRATION NUMBER

The study was registered at Clinical Trials Gov (NCT03555942).