Influence of the dominant follicle on in-vitro maturation of human oocytes: a prospective non-randomized study

The present study was designed to examine the influence of timing of aspiration and the influence of a dominant follicle on maturation and fertility potential of immature oocytes aspirated in unstimulated cycles. The study included 81 regularly cycling women. In group I (n = 53), oocyte retrieval was scheduled the day after a follicle of 10 mm and an endometrium of at least 5 mm were observed. In group II (n = 28), aspiration was scheduled the day after observation of the same ultrasound criteria plus a detected increase (100%) in the level of oestradiol compared with the level on day 3. The maturation rate was significantly higher in group I compared with group II (107/184, 58.2% versus 56/124, 45.2%, P < 0.05), whereas the rates of fertilization and cleavage did not differ between the two groups. The clinical pregnancy rate per aspiration was significantly higher in group I compared with group II (9/53, 17% versus 0/28, 0%, P < 0.05). When comparing oocytes originating from the ovary with the dominant follicle (ipsilateral ovary) with oocytes originating from the ovary without a dominant follicle (contralateral ovary) an increased fertilization rate was observed in group I, and an increased maturation rate was observed in group II. When the data from the two groups were pooled, an increased maturation rate was observed in oocytes originating from the ipsilateral ovary compared with oocytes originating from the contralateral ovary. No difference was found with respect to rates of fertilization and cleavage rates when all oocytes originating from the ipsilateral ovary were compared with all oocytes originating from the contralateral ovary.