Correlation between endometrial dating of luteal phase days 6 and 10 of the same menstrual cycle

Endometrial maturation, important in the diagnosis of infertile couples, has been evaluated since 1950 using the Noyes criteria. Nevertheless, there is no consensus regarding the most suitable period of the luteal phase for performing the biopsy. This study evaluated the correlation between the histological dating of two endometrial biopsies performed in the same menstrual cycle, on luteal phase days six and ten. Prospective study. Human Reproduction Division of the Federal University of São Paulo, referral center. Twenty-five women complaining of infertility had their menstrual cycles monitored by ultrasound and LH plasma levels, to obtain evidence of ovulation. Endometrial biopsies were performed on luteal phase days LH + 6 and LH + 10 (luteal phase day 1 = LH + 1 = the day that follows LH peak). Dating was done according to morphometric criteria, in which an endometrium sample is considered out of phase if the minimum maturation delay is one day. On day LH + 6, blood was drawn for plasma progesterone level determination. All patients had an ovulatory cycle (mean LH peak: 47.4 U/L; mean follicular diameter on LH peak day: 18.9 mm; mean endometrial thickness on LH peak day: 10.3 mm; mean plasma progesterone level on day LH + 6: 14.4 ng/ml). 14 patients had both biopsies in phase; 5 patients had out of phase biopsies only on day LH + 6; 3 had out of phase biopsies only on day LH + 10 and 3 patients had out of phase biopsies on both days. McNemar's test showed no statistical difference between these data (p > 33.36%). The correlation found between the endometrial datings suggests that biopsies performed on either of these two days are suitable for evaluation of endometrial maturation.