The window for embryo transfer in oocyte donation cycles depends on the duration of progesterone therapy

Abstract

In 192 oocyte donation cycles performed between January 1993 and July 1996, we examined the width of 'the window for embryo transfer' using standard hormonal replacement methods. All transfers were performed within 48 h of insemination. We varied the day of embryo transfer with regard to the initiation of progesterone therapy and, thus, the duration of endometrial exposure to progesterone and analysed the resulting pregnancy rates. Patients were divided into five groups (I-V) and embryo transfers were performed 2, 3, 4, 5 or 6 days following initiation of progesterone therapy. The number of pregnancies per transfer cycle achieved in groups I-V were 0 (0%), 3 (12%), 16 (40%), 29 (48.3%), and 10 (20.4%) respectively. The increased pregnancy rate in group III in comparison to group II is statistically significant (P < 0.03). Furthermore, the pregnancy rate in group IV (5 days of progesterone administration before embryo transfer) was significantly higher than in group V (6 days of progesterone administration before embryo transfer; P < 0.005). We also noted that, when embryos were transferred 4 or 5 days after initiation of progesterone therapy, the pregnancy rates were not significantly different between menopausal and cycling recipients (50% vs 43.7%). Our results indicate that the window for embryo transfer is dependent on duration of treatment with progesterone; it begins approximately 48 h after starting progesterone administration and lasts for approximately 4 days. The optimum period for transferring embryos at the 4- to 8-cell stage corresponds to cycle days 18 and 19. Transfers performed on the 17th and 20th days of the cycle can result in successful implantation, although the rates of implantation are highest when transfers are done on days 18 and 19.

Hormonal induction of endometrial receptivity

“…Prapas et al (40) transferred day-2 embryos while varying the P start so that transfers took place on day 2, 3, 4, 5, or 6 of P stimulation. Instead of optimal implantation rates on day 2 or 3 (as would be suggested by the preceding paragraph), they observed no pregnancies with transfers on day 2 and found optimal implantation rates to be associated with transfers on day 4 or 5 of P stimulation.…”

Human cleavage-stage embryo vitrification is comparable to slow-rate cryopreservation in cycles of assisted reproduction

“…Progesterone supplements (50 mg/day prontogest intramuscular injection) were administered 2-4 days before embryo transfer [16,17]. Both oestradiol valerate and progesterone supplements were continued until the pregnancy test.…”

Vitrification can modify embryo cleavage stage after warming. Should we change endometrial preparation?

“…In our study day 3 vitrified/warmed embryos, which after 24 h in culture had divided into cleavage stage, were transferred after 3 or 4 days of progesterone supplementation and no difference was observed in pregnancy or implantation rate (33.3 % vs 20 %). This finding would suggest that implantation of warmed embryos at cleavage stage do not benefit from a longer preparation with progesterone, as it had been defended in artificial cycles in egg donation [10,12,14]; although using frozen instead of fresh embryos may account for differences observed.…”

“…In in vitro fertilization cycles the high levels of oestradiol will accelerate endometrial development and the appearance of pynopodes one or two days compared to natural cycles, although this may vary depending on hormonal treatment and individuals [6,11,19]. In egg donation treatment with oestradiol /progesterone supplemented cycles, some authors have observed that pynopode formation in these cycles is similar to natural cycles [7], while others suggest that the preparation of the endometrium is 2 or 3 days slower than in natural cycles [10,12,14]. In frozen embryo transfer cycles the optimal progesterone supplementation before transfer is still debated.…”