The effect of the levonorgestrel intrauterine system on uterine artery blood flow 1 year after insertion.

Abstract

To assess whether the morphological alterations of the endometrium induced by the levonorgestrel intrauterine system affect the uterine artery vasculature. Forty-eight premenopausal women attending our gynecology clinic because of menorrhagia were enrolled into the study. Clinical measures of menstrual bleeding, endometrial thickness and Doppler flow of the uterine artery (resistance (RI) and pulsatility (PI) indices) were evaluated before and 1 year after insertion of the levonorgestrel intrauterine system. Thirty-three (69%) women were available for re-evaluation at the end of the first year and the continuation rate was 76% (n = 25). A paired samples t-test and the Mann-Whitney U-test were used for comparison of values between groups. The mean age of the thirty-three patients was 44.3 +/- 7.6 years. Nine patients (27.3%) were amenorrheic and three patients were in menopause at the end of the year. After excluding the women in menopause, the increase in mean RI 1 year after insertion was statistically significant (0.86 +/- 0.07 vs. 0.81 +/- 0.08; P = 0.046), as was the decrease in uterine volume (736.9 +/- 276.9 mL vs. 972.75 +/- 465.71 mL; P = 0.029). The mean endometrial thickness decreased 1 year after insertion, but not significantly (4.6 +/- 1.6 mm vs. 6.6 +/- 3.5 mm; P = 0.07) and there was no statistically significant difference in mean PI between the groups (2.00 +/- 0.63 and 2.03 +/- 0.64 pre- and post-insertion, respectively; P = 0.83). The increase in mean RI of the uterine artery and the decrease in uterine volume 1 year after insertion of the levonorgestrel intrauterine system may be related to its progestational effect. This increase in RI may have a role in cessation of menstruation.