Table 2.
Estimated Effect of Pregnancy on Time to Virological Failure Among 7,534 HIV-Positive Women Initiating Highly Active Antiretroviral Therapy in South Africa, 2004–2011
| R1 | R0 | RD (R1 − R0), % | 95% CI | |
|---|---|---|---|---|
| Exposure RD | Always | Never | 10.1 | 4.6, 15.6 |
| Population attributable RD | Observed | Never | 1.3 | 0.0, 2.6 |
| Generalized impact RDa | ||||
| Intervention 1 | Observed | Reduceda | 0.5 | −0.5, 1.6 |
| Intervention 2 | Observed | Reduceda | 0.5 | −0.5, 1.6 |
| Intervention 3 | Observed | Reduceda | 1.0 | −0.1, 2.0 |
| Targeted impact RDb | Observed | Reducedb | 0.6 | −0.5, 1.6 |
Abbreviations: CI, confidence interval; DMPA, depot-medroxyprogesterone acetate; HIV, human immunodeficiency virus; RD, risk difference.
a Interventions 1, 2, and 3 are described in the text. Briefly, intervention 1 lowers the per-month risk of pregnancy by 62% in all women; intervention 2 lowers the risk of pregnancy to 0 over the entire follow-up period in 62% of women; and intervention 3 allows women to use DMPA at any time; if they do so, they do not become pregnant for 3 months.
b Also described more fully in the text; here, we elaborate on intervention 3 (above) such that younger women are more likely to use DMPA.