Effects of oral contraceptive, synthetic progestogen or natural estrogen pre-treatments on the hormonal profile and the antral follicle cohort before GnRH antagonist protocol

BACKGROUND: Steroid pre-treatments may be useful to program GnRH antagonist IVF/ICSI cycles. This prospective study assessed hormonal and ultrasound data collected during the free period after the discontinuation of three different pre-treatments to provide information on the optimal time interval required before starting stimulation. METHODS: Women were randomized to receive oral contraceptive pill (OCP) [ethinyl estradiol (E2) 30 µg + desogestrel 150 µg] (n = 21) or norethisterone 10 mg/day (n = 23) or 17-βE2 4 mg/day (n = 25) or no pre-treatment (n = 24) for one cycle before IVF. Assessments were performed on post-treatment day (PD) 1, 3 and 5, or on spontaneous cycle day (CD) 1 and 3. RESULTS: After OCP and progestogen administration, FSH and LH concentrations shifted from strongly suppressed PD1 levels to PD5 values similar to those observed on CD1. Meanwhile, follicle sizes remained small up to PD5. In contrast, estrogen pre-treatment poorly reduced FSH levels on PD1 compared with OCP or progestogen. Consequently, follicle size was more heterogeneous. FSH rebound was maximal on PD3, whereas LH levels were slightly increased up to PD5. CONCLUSIONS: A 5-day free interval after OCP or progestogen offers the advantages of gonadotrophin recovery and homogeneous follicular cohort, whereas early FSH rebound occurring after estrogen pre-treatment argues for a short free period.