Endometrial morphology and peripheral hormone levels in women with regular menstrual cycles.

Endometrial biopsies from 90 women with regular menstrual cycles and a hormonal profile compatible with normal luteal function were morphometrically assessed using 11 different indices and the results were plotted in 48-hour periods around the day of the luteinizing hormone (LH) surge (LH +/- 0). The endometrial dating reached its highest significance from days LH -3/-2 to days LH +7/+8, when the changes occurred with a high degree of regularity regardless of the length of the preovulatory and postovulatory phases. It is proposed therefore that the dating of the endometrium should be related to the LH surge rather than to the "ideal" 28-day cycle. The results also seem to suggest the existence of a regulatory mechanism for the synchronization of follicular maturation and midcycle endometrial development. Further study of the factors involved in this mechanism may result in a better understanding of certain forms of unexplained infertility.