The Effect of Age,Parity and Body Mass Index on the Efficacy,Safety, Placement and User Satisfaction Associated With Two Low-Dose Levonorgestrel Intrauterine Contraceptive Systems: Subgroup Analyses of Data From a Phase III Trial

Objective

Two low-dose levonorgestrel intrauterine contraceptive systems (LNG-IUSs; total content 13.5 mg average approx. 8 μg/24 hours over the first year; LNG-IUS 8] and total content 19.5 mg average approx. 13 μg/24 hours over the first year; LNG-IUS 13]) have previously been shown to be highly effective (3-year Pearl Indices: 0.33 and 0.31, respectively), safe and well tolerated. The present subgroup analyses evaluated whether or not outcomes were affected by parity, age (18–25 vs 26–35 years), or body mass index (BMI, <30 vs ≥30 kg/m²).

Methods

Nulliparous and parous women aged 18‒35 years with regular menstrual cycles (21‒35 days) requesting contraception were randomized to 3 years of LNG-IUS 8 or LNG-IUS 13 use.

Results

In the LNG-IUS 8 and LNG-IUS 13 groups, 1432 and 1452 women, respectively, had a placement attempted and were included in the full analysis set; 39.2%, 39.2% and 17.1% were 18–25 years old, nulliparous and had a BMI ≥30 kg/m², respectively. Both systems were similarly effective regardless of age, parity or BMI; the subgroup Pearl Indices had widely overlapping 95% confidence intervals. Placement of LNG-IUS 8 and LNG-IUS 13 was easier (p < 0.0001) and less painful (p < 0.0001) in women who had delivered vaginally than in women who had not. The complete/partial expulsion rate was 2.2–4.2% across all age and parity subgroups and higher in parous than in nulliparous women (p = 0.004). The incidence of pelvic inflammatory disease was 0.1–0.6% across all age and parity subgroups: nulliparous and younger women were not at higher risk than parous and older women, respectively. The ectopic pregnancy rate was 0.3–0.4% across all age and parity subgroups. Across all age and parity subgroups, the 3-year completion rate was 50.9–61.3% for LNG-IUS 8 and 57.9–61.1% for LNG-IUS 13, and was higher (p = 0.0001) among older than younger women in the LNG-IUS 8 group only.

Conclusions

LNG-IUS 8 and LNG-IUS 13 were highly effective, safe and well tolerated regardless of age or parity.

Trial Registration

Clinical trials.gov NCT00528112