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.