What is the endometrial thickness in premenopausal women?

• A. 1.5 cm (15 mm)
• B. <5 mm
• C. <8 mm
• D. 2 cm

Answer: (A)

In premenopausal women, endometrial thickness changes with the menstrual cycle, peaking during the secretory phase when the lining thickens in preparation for possible implantation. Transvaginal ultrasound shows a broad normal range: roughly a few millimeters early in the cycle, increasing to about 10–12 mm in the late proliferative phase, and often reaching around 15 mm or slightly more in the secretory phase. A measurement of 15 mm sits right in this normal upper range for premenopausal states, reflecting the thickened secretory endometrium.

Less than 5 mm is typically seen in postmenopausal or atrophic endometrium, not in a typical premenopausal cycle. Less than 8 mm could occur in early proliferative phases but doesn’t capture the common peak thickness. Two centimeters (20 mm) is at the higher end and less commonly encountered as a normal peak, though it can occur. Therefore, 15 mm best represents a normal premenopausal endometrial thickness.