Impact of Timing of Antiretroviral Treatment and Birth Weight on Mother-to-Child Human Immunodeficiency Virus Transmission: Findings From an 18-Month Prospective Cohort of a Nationally Representative Sample of Mother-Infant Pairs During the Transition From Option A to Option B+ in Zimbabwe.

BACKGROUND

Preventing mother-to-child transmission of human immunodeficiency virus transmission (MTCT) depends on early initiation of antiretroviral therapy (ART). We report the 18-month MTCT risk during the transition from Option A to Option B+ in Zimbabwe, and assess whether ART preconception could eliminate MTCT in breastfeeding populations.

METHODS

In 2013, we consecutively recruited a nationally representative sample of 6051 infants aged 4-12 weeks and their mothers from 151 immunization clinics using a multistage stratified cluster sampling method. We identified 1172 human immunodeficiency virus (HIV)-exposed infants and evaluated them at baseline and every 3 months until the child became HIV-infected, died, or reached age 18 months.

RESULTS

The cumulative MTCT risk through 18 months postdelivery was 7.0%. Of the HIV-infected mothers, 35.3% started ART preconception, 28.9% during pregnancy, and 9.7% after delivery, and 16.0% received zidovudine during pregnancy. Compared to mothers without antiretroviral drug use, MTCT among those starting ART preconception and during pregnancy was lower by 88% (adjusted hazard ratio [aHR], 0.12; 95% confidence interval [CI], .06-.24) and 75% (aHR, 0.25; 95% CI, .14-.45), respectively. HIV-exposed infants with birth weight <2.5 kg (low birth weight) were 2.6-fold more likely to acquire HIV infection compared to those with birth weight ≥2.5 kg (aHR, 2.57; 95% CI, 1.44-4.59). Controlling for other factors, breastfeeding was not significantly associated with MTCT.

CONCLUSIONS

ART preconception has the highest impact on reducing MTCT, indicating that HIV-infected, reproductive-age women should be prioritized in "treat-all" strategies. HIV-infected mothers without ART use should be identified at the first immunization visit and treatment initiated to reduce postdelivery MTCT. MTCT risk is higher in mothers with low-birth-weight deliveries.