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The LNG-IUS and IUD are both highly effective, but one is associated with changes in uterine artery blood flow.
Two long-acting reversible contraceptive methods-the levonorgestrel-releasing intrauterine system (LNG-ISU) and the copper intrauterine device (IUD)-are highly effective and safe in preventing pregnancies.
But what impact do these two contraceptive techniques have on menstrual changes and uterine artery Doppler indices?
A randomized clinical trial conducted at Menoufia University Hospital in Egypt between December 2016 and August 2017 found that LNG-IUS-related abnormal bleeding is associated with changes in uterine artery blood flow, but the same changes are not seen in women with copper IUDs.
“Uterine artery Doppler is a simple, inexpensive, and readily available tool to assess women with abnormal uterine bleeding after insertion of the LNG-IUS for contraception,” wrote the authors about their study in The International Journal of Obstetrics & Gynecology.
The investigators said changes in the uterine vasculature of IUD users are important for clinicians to understand, so they can help counsel women about their contraceptive choices.
For the study, 306 multiparous women with a normal menstrual cycle who wanted intrauterine contraception were randomly assigned to either an LNGâIUS (n = 152) or a copper IUD (n = 154). The uterine artery pulsatility index (PI) and the resistant index (RI) were measured before contraceptive use and at 3 and 6 months after insertion.
Irregular bleeding was initially reported by 74% of women in the LNGâIUS group, and heavy menstrual bleeding by 67% of women in the copper IUD group.
Incidence of abnormal bleeding in both groups decreased over the 6âmonth study period; however, a higher percentage of women in the copper IUD group reported lower abdominal pain, back pain and abnormal bleeding at the end of the study period (P > 0.001). But fewer women in the LNG-IUS group reported abnormal bleeding at the start of the study (P > 0.001): 27.6% versus 51.3% in the copper IUD group.
“There was a significant difference between the two groups in initial PI (P > 0.001) and RI (P > 0.001), which were both high among women in the LNG-IUS group,” wrote the authors. Yet in both groups, the PI and the RI were dramatically lower at the 3- and 6-month intervals in comparison to the initial Doppler indices (all P > 0.001):
Uterine artery PI also significantly correlated with abnormal bleeding at a cutoff of 1.35 with area under the curve (AUC) 0.93, sensitivity 88% and specificity 100%. Similarly, there was a meaningful connection between the uterine artery RI and abnormal bleeding at a cutoff of 0.62 with AUC 0.1, sensitivity 96% and specificity 100%.
The investigators noted that most recent studies of the copper IUD have reported no significant changes in uterine artery PI and RI, with or without adverse events like dysmenorrheal, heavy menstruation, and dyspareunia at 3 or 6 months after insertion.
“Heavy menstrual bleeding associated with the copper IUD might be due to induced production of vasoactive agents other than prostaglandins in the surrounding tissue,” the authors wrote.
Two limitations of the current study are a shorter follow-up period and lack of comparison to other long-acting contraceptive methods.
The authors concluded that future research should concentrate on the predictive value of uterine artery Doppler indices and the ensuing heavy menstruation among new users of the copper IUD.