High fecundity of amenorrhoeic women in embryo-transfer programmes.

There is uncertainty over whether the steady decline in human fertility with increasing maternal age is due to quality of the oocyte or of the endometrium. To clarify the issue age-related implantation and pregnancy rates in two embryo-transfer programmes were examined in relation to embryo quality and type of menstrual cycle. In both the UK and the US programmes rates were higher in previously amenorrhoeic (acyclic) women than in eugonadal women, irrespective of age and number of embryos replaced. Oocyte quality, as determined by age of oocyte donor, in-vitro growth of embryo, and proportion of defective embryos in culture, did not contribute to the difference, nor did type of cycle during therapy. If a uterus that has not been subjected to regular menstrual cycles is a favourable factor, a period of induced amenorrhoea might be beneficial for infertile women.