Exogenous progestogen does not affect first-wave follicle populations and oocyte quality during ovarian stimulation with FSH in sheep.

The effect of short-term administration of medroxyprogesterone acetate (MPA) or natural progesterone (P ₄ ) during ovarian stimulation with FSH on oocyte recovery was investigated in Santa Inês ewes. Ewes were treated with an intravaginal sponge containing MPA for 6 d; GnRH was applied 36 h after sponge removal and FSH was given in 3 injections (40, 24, and 16 mg, respectively) every 12 h after (D0, approximate ovulation time). At the first FSH dose, the ewes received either a new MPA sponge (n = 10) or a controlled device for internal release impregnated with P ₄ (n = 10) or did not receive any device (n = 10). Ovarian dynamics were assessed every 12 h by transrectal ultrasonography from D-3 to D2. Oocytes were recovered by laparoscopic ovum pick-up (LOPU) on D2 and graded by morphologic quality. The number of small, medium, and large follicles at D0 and D2 (ultrasound examinations), number of both follicles aspirated and oocytes recovered at LOPU, recovery rate, and oocyte grade did not differ (P > 0.05) among treatments. Thus, the short-term use of MPA or P ₄ during ovarian stimulation did not affect the first-wave follicle population or morphologic quality of oocytes. We would suggest that, in this protocol, the use of exogenous progestin is unnecessary.
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