Accuracy of endometrial biopsy dating in relation to the midcycle luteinizing hormone peak

The accuracy of endometrial biopsy dating was evaluated in a selected group of apparently normal women in whom the basal body temperature (BBT), the onset of subsequent menstruation, the midcycle luteinizing hormone (LH) peak, and the 17beta-estradiol peak were determined. Forty-two women with regular cycles, normal ovaries at laparoscopy, and luteal phases of 12 to 15 days were studied. In group I (n=20), the infertility could be explained satisfactorily by either tubal occlusion or infertility of the husband, while in group II (n=22) no explanation was found for the infertility. In group I the duration of the luteal phase, defined as the interval between the LH peak and the onset of subsequent menstruation, was 13.4+/-0.7 days. The plasma 17beta-estradiol concentration declined (P less than 0.01) on the day of the LH peak in both groups of women, while the first significant rise (P less than 0.05) in BBT occurred in groups I and II, respectively, 1 and 2 days following the LH peak. Dating of the endometrial biopsy correlated with the LH peak with standard deviations of 1.2 and 1.3 days, respectively, in groups I and II. It is suggested that, in women with a progressive rise in BBT over several days, the localization of the LH peak can be helpful for correct interpretation of the endometrial biopsy.