Possible factors affecting the development of oocytes in in-vitro maturation

To date, pregnancy rates from oocytes matured in-vitro (IVM) have been much lower than those with in-vivo stimulated maturation. In order to improve the developmental potential of IVM oocytes, we studied the effect of three possible factors on pregnancy rates: (i) priming in vivo with FSH before aspiration; (ii) the time interval of maturation in vitro, and (iii) timing the aspiration by monitoring the serum concentrations of oestradiol and inhibin A. In all experiments, oocyte retrieval was performed transvaginally and oocytes were matured individually in culture medium (TCM 199) under oil. Intracytoplasmic sperm injection (ICSI) was carried out on all metaphase II oocytes. Suitable embryos (maximum of two) were replaced after culturing for 2-3 days in IVF medium. Endometrial priming consisted of 2 mg 17beta-oestradiol, taken orally three times a day from the day of oocyte retrieval, and intravaginal progesterone suppositories initiated 2 days later. In the first experiment, 20 women were randomly allocated to two groups: group I (n = 10 cycles) received no stimulation, while group II (n = 10 cycles) received recombinant FSH 150 IU/day for 3 days, initiated on day 3. FSH priming did not affect the rates of maturation, fertilization or cleavage, and no effect was seen on embryo development. The second experiment included 48 patients undergoing 55 unstimulated cycles. The effects of IVM periods of 28 and 36 h were compared. Shortening the IVM period did not compromise subsequent embryo development. The third study analysed the results of maturation of oocytes obtained in 87 cycles in 75 unstimulated normal women, after a leading follicle of 10 mm in diameter and an endometrial thickness of at least 5 mm were observed. A pregnancy rate of 12.6% (11/87) per aspiration and 17.4% (11/63) per transfer was obtained. Serum concentrations of oestradiol and inhibin A were evaluated retrospectively. Significantly more pregnancies were obtained in cycles with a detected increase in the concentration of oestradiol from day 3 to the day of aspiration (19% per aspiration) compared with cycles without such an increase (0% per aspiration). A higher pregnancy rate was observed after an increase in inhibin A concentration (24 versus 0%). In conclusion, monitoring the timing of aspiration may potentially improve the developmental potential of immature oocytes. FSH priming did not affect either cleavage rate or embryo development. Shortening the maturation period from 36 to 28 h did not compromise subsequent embryonic development.