Table 2.
Contraceptive Effectiveness Measured by Pearl Index and 95% Confidence Interval among Participants Receiving Injections in the Abdomen and Upper Thigh.
| No. of Women | Person Years | No. of Pregnancies | Pearl Index (per 100 WY) | 95% CI for Pearl Index | |
|---|---|---|---|---|---|
| Primary Effectiveness1 | 682 | 629.3 | 0 | 0.00 | (0.00, 0.59) |
| Perfect Use2 | 680 | 592.7 | 0 | 0.00 | (0.00, 0.62) |
| Sensitivity Analysis3 | 682 | 500.5 | 0 | 0.00 | (0.00, 0.74) |
28 out of 710 women were censored at enrollment and are not included in this count. 10 were lost to follow-up, 17 discontinued early without a pregnancy test, and 1 was already pregnant at enrollment.
30 out of 710 women were censored from the Perfect Use analysis at enrollment and are not included here.
Pearl Index computed using a conservative scenario in terms of person-time. Approximately 14% of women in the PK cohort had baseline MPA >= 0.05 ng/mL. Also 81.4%, 84.2%, and 85.5% of women reported having sex in the previous 4 weeks (time most at risk) and having no condom use since last injection for baseline, month 4, and month 8 injection cycles respectively. Based on these estimates, we included 70% (86%*81.4%) of WY contributed in the first injection cycle, and 84.2% and 85.5% of WY contributed in the second and third injection cycles, respectively.