Defining endometrial growth during the menstrual cycle with three‐dimensional ultrasound

Objective  To define the changes in endometrial morphometry that occur during the normal menstrual cycle and to examine the discriminatory power of volumetric analysis over conventional two‐dimensional measurements in quantifying the effect of compounding factors on endometrial growth. Design  The design was that of a longitudinal observational study. Subjects were seen on an alternate‐day basis until ovulation and then every four days until the next menstrual period. Setting  A University teaching hospital. Population  Thirty women with regular cycles and acceptable ‘normal’, menstrual patterns. Methods  Three‐dimensional ultrasound data were acquired and subsequently analysed by a single observer. Main outcome measures  Endometrial thickness and volume. Results  Both endometrial volume and thickness increased significantly during the follicular phase ( P < 0.001), reaching a plateau around the time of ovulation and remaining relatively stable throughout the luteal phase. These changes in endometrial thickness and volume were highly correlated ( R 2 = 0.767; P < 0.001). Parity was associated with a significantly greater endometrial volume than nulliparity (4.159 vs 2.234 cm 3 ; P < 0.05). Conclusions  This study has defined the relative and absolute changes in endometrial growth, both in terms of thickness and volume, throughout the normal menstrual cycle. These data provide a reference for future three‐dimensional studies investigating menstrual disorders, pathophysiological change and subfertility.