Risk factors for perinatal HIV-1 transmission in pregnant women requiring lifelong antiretroviral therapy: A longitudinal study at a tertiary hospital in South Africa

Abstract

Objectives. To estimate the infant HIV-1 transmission rate and to evaluate risk factors for transmission in pregnant women at an Eastern Cape tertiary hospital requiring lifelong antiretroviral therapy (ART). Methods. Pregnant women who initiated lifelong ART during pregnancy and others who conceived on lifelong ART were followed up antenatally, through delivery, until 6 weeks postpartum. A qualitative HIV-1 DNA polymerase chain reaction (PCR) was done on the infants at 6 weeks. Risk factors evaluated for perinatal HIV transmission included CD4 count, duration of ART, plasma HIV-1 RNA viral load (VL) at delivery, preterm birth, and mode of delivery. Results. Data on 838 women with 858 live births are presented. The median CD4 count was 192 cells/μl, and the median duration of ART was 12 weeks. Of 618 women (73.7%) with VL results at delivery, 555 women (89.8%) had a VL <1 000 copies/ml. HIV-1 DNA PCR was performed on 665 out of 831 infants (80%) from 6 weeks onwards. Transmission occurred in 16 infants (2.4%; 95% confidence interval (CI) 1.4 - 4.0). The transmission rate was 7.8% with maternal plasma VL ≥1 000 copies/ml (p=0.018), 4.2% with duration of ART <10 weeks (p=0.010), and 8.6% with preterm birth (p=0.046). On multivariable regression analysis VL ≥1 000 copies/ml (adjusted odds ratio (AOR) 12.82; 95% CI 1.72 - 95.53) and duration of ART <10 weeks (AOR 4.91; 95% CI 1.40 - 17.18) remained significant predictors of transmission. Conclusions. Maternal plasma VL at delivery and duration of ART are significant independent predictors of perinatal HIV-1 transmission, but transmission can occur with undetectable plasma VL at delivery.