Fourth World Conference on Early Pregnancy CONTINUUM BETWEEN IMPLANTATION AND PERINATAL EVENTS

Mechanisms In Implantation: Oestrogen Revisited Lessons From Ovarian Hyperstimulation Syndrome

Gedis Grudzinskas

Presentation

Improvement in the implantation rate following ART will continue with the success of new strategies for better embryo selection and the use of blastocyst culture. Endometrial receptivity is presumed to be little influenced by few factors, other than a minimum of six days exposure to oestrogen if followed by progesterone in a well regulated regime. Curiously, it has been argued that a prolonged period of relative oestrogen deprivation may sensitise endometrial receptivity to the effects of hormonal changes that occur in the treatment cycle, as argued from the high pregnancy rates following ART in women with premature menopause or prolonged down-regulation.

Detailed studies in women at risk of severe OHSS, who have undergone withholding of gonadotrophin stimulation(coasting) for up to 13 days before oocyte collection have provided a model for studies on granulosa cell, oocyte and endometrial functions. As we have observed an implantation rate of 20% per embryo transferred, we have analysed our data with respect to serum oestrogen(E₂) levels after the function embryonic development etc to review the traditional coverage on the window of implantation. The overall clinical pregnancy rate in 73 women who underwent coasting (mean 4.9 days) was 28.9 per cycle commenced, 33.3% per Embryo Transfer procedure,the implantation rate being 20.3% per embryo transferred. The clinical pregnancy rate was equivalent in relation to the duration of coasting, aetiology of infertility (PCOS n = 28, male factor n = 35, tubal disease n = 9.) and ... Only 3 of 73 women were hospitalised with severe OHSS, two of whom were protocol violations receiving their hCG trigger before serum E2 levels fell below 10,000 pmol/l.

We are able to make the following preliminary conclusions, firstly ,prolonged coasting with substantially reduce the number of with women severe OHSS, secondly, this can be achieved whilst maintaining a high clinical pregnancy rate, thirdly, we can challenge the traditional views on the implantation window. Thus it is appropriate to reconsider the traditional views on the following:

a) strategies of Controlled Ovarian Hyperstimulation(COH) which are inflexible with respect to FSH administration.

b) the view that relative oestrogen restriction is helpful prior to commencing COH, as one third of our patients had PCOS a state of hyperoestrogenism

c) prolonged coasting does lead to a reduction in oocyte function.

Currently, studies using techniques in the rapidly advancing field of proteomics are being systematically applied to examining these events.

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