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 mug/24 hours over the first year; LNG-IUS 8] and total content 19.5 mg [average approx. 13 mug/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 kg/m2). METHODS: Nulliparous and parous women aged 1835 years with regular menstrual cycles (2135 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.