Effect of the Yuzpe regimen of emergency contraception on markers of endometrial receptivity.

This exploratory study was designed to determine whether treatment with the Yuzpe regimen of emergency contraception altered endometrial integrin expression or other markers of uterine receptivity. Nineteen parous women were followed for two menstrual cycles. In the second cycle, each participant took 100 mg ethinyl oestradiol and 1 mg norgestrel on the day of the urinary luteinizing hormone (LH) surge and repeated the dose 12 h later. In both cycles, endometrial biopsy, phlebotomy and vaginal sonogram were performed 8-10 days after the urinary LH surge. No significant difference was found between untreated and treated cycles in most measures of endometrial histology or in endometrial expression of beta3 integrin subunit, leukaemia inhibitory factor, glycodelin, or progesterone receptors assessed by immunohistochemical techniques. Five statistically significant changes were noted in treated cycles: a reduction in endometrial MUC-1 expression, an increase in endometrial oestrogen receptor, lower luteal phase serum oestrogen concentration, reduced endometrial thickness, and greater proportion of glandular supranuclear vacuoles. The relationship of these findings to the contraceptive action of the Yuzpe regimen is unclear.