The impact of endometrioma size on ovarian responsiveness

Available evidence shows that the presence of ovarian endometriomas does not interfere with the ovarian response to ovarian stimulation. However, the mean size of the endometriomas in these studies is generally small, and two recent investigations suggested that follicular development could be impaired when focusing on larger endometriomas. However, these studies could not identify a clear threshold above which endometriomas could become detrimental.

To identify this threshold, the study retrospectively selected women without a history of surgery for ovarian cysts who underwent IVF in the presence of unilateral endometriomas with a mean diameter between 20 and 49 mm. Selected women were divided into three categories of endometrioma size: 20-29 mm (group 1, n = 23), 30-39 mm (group 2, n = 2323), and 40-49 mm (group 3, n = 2321). Recruitment for each category was censored at about 21 women to ensure equal statistical power for each group.

The response to ovarian stimulation was equal or superior in the affected gonads in eight women (35%, 95% confidence interval [CI] 16-57%), seven women (30%, 95% CI 13-53%) and two women (10%, 95% CI 2-30%) in groups 1, 2 and 3, respectively. The median (interquartile range) number of developed follicles in the affected and intact ovaries was 6 (3-7) and 5 (4-9) in group 1 (P = 0.21), 4 (1-6) and 4 (3-7) in group 2 (P = 0.08), 5 (3-7), and 7 (4-8) in group 3 (P = 0.01), respectively.

The threshold to be used to distinguish between endometriomas that might and might not interfere with ovarian response is 4 cm in diameter.