Dating the endometrial biopsy by flow cytometry.
OBJECTIVE: To determine endometrial changes throughout the menstrual cycle. DESIGN: Flow cytometric analysis of endometrial cells versus chronological dating. SETTING: Women volunteers with a normal menstrual cycle participated in this study that was done in an academic research environment. PATIENTS: Two hundred thirty regular menstruating women with adequate luteal phase underwent endometrial biopsy at different days of their menstrual cycle; 138 biopsies were analyzed both histologically and by flow cytometry. MAIN OUTCOME MEASURE: Percentage of biopsies correctly classified in terms of chronological dating. RESULTS: Flow cytometry correctly classified the chronological day of biopsies in 59% of cases, the proliferative versus secretory days in 91% of cases, and the early, mid, and late secretory phases of the menstrual cycle were correctly predicted in 86% of cases. CONCLUSION: Flow cytometry is a good method to determine growth and differentiation of the endometrium during the menstrual cycle. Detection of phases of the whole endometrial cell population offer information on the biological adequacy of endometrial response to the biochemical environment.