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 taking lifelong antiretroviral therapy (ART) at an Eastern Cape tertiary hospital.

Methods. Pregnant women 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 infant at 6 weeks. Risk factors evaluated for perinatal HIV-1 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. Median CD4 count was 192 cells/ul, and median duration of ART was 12 weeks. Of 618 women (74%) with VL results at delivery, 555 women (90%) had VL <1000 copies/mL.
HIV-1 DNA PCR was performed on 665 out of 831 infants (80%) from 6 weeks onwards. HIV-1 transmission occurred in 16 infants (2.4%; 95% confidence interval [CI] 1.4–4.0). Transmission rate was 7.8% with maternal plasma VL ≥1000 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 logistic regression analysis VL ≥1000 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 HIV-1 transmission can occur with undetectable plasma VL at delivery.