Table 2.

Pregnancy incidence per 100 women-years, grouped by contraceptive method and antiretroviral therapy (ART) regimen combinations

Contraceptive method and ART regimen combinations	Number of pregnancies	Women-years of follow-up	Unadjusted pregnancy rate§ per 100 women- years (95% CI)	Adjusted pregnancy rate# per 100 women- years (95% CI)	Adjusted pregnancy rate ratios# per 100 women-years (95% CI)
Implant	86	3047	3.0 (2.3–3.6)*	1.4 (1.1–1.8)**
Nevirapine-based ART	34	1648	2.2 (1.4–2.9)	1.1 (0.72–1.5)	Ref.
Efavirenz-based ART	21	375	5.8 (3.3–8.4)	3.3 (1.8–4.8)	3.0 (1.3–4.6)
Lopinavir/ritonavir-based ART	2	126	1.7 (0–4.1)	0.95 (0–2.3)	0.86 (0–2.1)
No ART	29	897	3.4 (2.1–4.6)	1.3 (0.82–1.8)	1.2 (0.60–1.8)
Depomedroxyprogesterone acetate (DMPA)	631	7406	8.9 (8.2–9.6)*	4.3 (3.7–4.9)**
Nevirapine-based ART	320	3983	8.4 (7.5–9.3)	4.5 (3.7–5.2)	Ref.
Efavirenz-based ART	76	842	9.4 (7.3–11.5)	5.4 (4.0–6.8)	1.2 (0.91–1.5)
Lopinavir/ritonavir-based ART	20	299	7.2 (4.1–10.3)	4.5 (2.5–6.5)	1.0 (0.56–1.5)
No ART	215	2275	9.8 (8.5–11.0)	3.9 (3.2–4.6)	0.87 (0.72–1.0)
Combined oral contraceptives or oral contraceptive pills (COCs or OCPs)	95	850	11.7 (9.4–14.1)*	5.8 (4.5–7.2)**
Nevirapine-based ART	46	443	10.9 (7.8–14.0)	5.8 (4.0–7.6)	Ref.
Efavirenz-based ART	17	115	15.4 (8.2–22.6)	9.3 (4.6–14.0)	1.6 (0.69–2.5)
Lopinavir/ritonavir-based ART	4	32	15.4 (0.54–30.2)	7.6 (0.18–14.9)	1.3 (0–2.6)
No ART	28	260	11.1 (6.9–15.3)	4.7 (2.9–6.6)	0.81 (0.43–1.2)
Other more effective contraception (IUDs, permanent)	17	1327	1.3 (0.69–1.9)*	1.1 (0.56–1.6)**
Nevirapine-based ART	8	767	1.1 (0.33–1.8)	0.92 (0.28–1.6)	Ref.
Efavirenz-based ART	2	217	0.93 (0–2.2)	0.93 (0–2.2)	1.0 (0–2.6)
Lopinavir/ritonavir-based ART	1	68	1.6 (0–4.6)	1.7 (0–5.1)	1.9 (0–5.8)
No ART	6	273	2.3 (0.47–4.1)	1.5 (0.29–2.7)	1.6 (0–3.3)
Less effective contraception (condoms, “natural” methods)	1739	14028	13.1 (12.5–13.7)*	5.6 (4.6–6.6)**
Nevirapine-based ART	957	8113	12.5 (11.7–13.3)	5.7 (4.7–6.8)	Ref.
Efavirenz-based ART	202	2077	10.1 (8.7–11.5)	5.4 (4.2–6.5)	0.94 (0.79–1.1)
Lopinavir/ritonavir-based ART	67	570	12.7 (9.7–15.7)	6.6 (4.7–8.5)	1.2 (0.87–1.4)
No ART	513	3262	16.6 (15.1–18.0)	5.4 (4.4–6.5)	0.95 (0.84–1.1)
No contraceptive method	762	10837	7.4 (6.8–7.9)*	4.8 (3.9–5.8)**
Nevirapine-based ART	351	5681	6.5 (5.8–7.2)	4.7 (3.7–5.6)	Ref.
Efavirenz-based ART	98	2111	4.8 (3.8–5.7)	4.0 (3.0–5.1)	0.86 (0.67–1.1)
Lopinavir/ritonavir-based ART	29	480	6.4 (4.0–8.8)	5.2 (3.0–7.4)	1.1 (0.68–1.6)
No ART	284	2555	11.6 (10.2–13.0)	5.3 (4.2–6.5)	1.1 (0.96–1.3)
Overall	3,330¶	37,495	8.9 (8.6–9.2)

^§Stratified rates by ART regimen calculated with an unadjusted Poisson model that included an interaction term between contraceptive method and ART regimen.

^#Stratified rates by ART regimen calculated with an adjusted Poisson model that included an interaction term between contraceptive method and ART regimen and covariates adjusted for included age, educational attainment, marital status, number of living children, HIV-positive status disclosure to partner, and time-dependent covariates of percent use of condoms, body mass index (BMI), World Health Organization (WHO) stage, CD4 cell count, and use of anti-tuberculosis medications during the observation period.

^*Unadjusted rates by contraceptive method calculated with an unadjusted Poisson model without ART regimen or an interaction term between contraceptive method and ART regimen.

^**Adjusted rates by contraceptive method calculated with ART regimen (but not an interaction term between contraceptive method and ART regimen) and covariates adjusted for included age, educational attainment, marital status, number of living children, HIV-positive status disclosure to partner, and time-dependent covariates of percent use of condoms, body mass index (BMI), World Health Organization (WHO) stage, CD4 cell count, and use of anti-tuberculosis medications during the observation period.

^¶Seven pregnancies occurred in observations where the contraceptive method was missing (in seven different women).