Introduction: Plasma HIV viral load (VL) is the principle determinant of mother-to-child HIV transmission (MTCT), yet there are few data on VL in populations of pregnant women in sub-Saharan Africa. We examined the distribution and determinants of VL in HIV-positive women seeking antenatal care (ANC) in Cape Town, South Africa.
Methods: Consecutive HIV-positive pregnant women making their first antenatal clinic visit were recruited into a cross-sectional study of viraemia in pregnancy, including a brief questionnaire and specimens for VL testing and CD4 cell enumeration.
Results & discussion: Overall 5551 pregnant women sought ANC during the study period, of whom 1839 (33%) were HIV positive and 1521 (85%) were included. Approximately two-thirds of HIV-positive women in the sample (n=947) were not on antiretrovirals at the time of the first ANC visit, and the remainder (38%, n=574) had initiated antiretroviral therapy (ART) prior to conception. For women not on ART, the median VL was 3.98 log10 copies/mL; in this group, the sensitivity of CD4 cell counts ≤350 cells/µL in detecting VL>10,000 copies/mL was 64% and this increased to 78% with a CD4 threshold of ≤500 cells/µL. Among women on ART, 78% had VL<50 copies/mL and 13% had VL >1000 copies/mL at the time of their ANC visit.
Conclusions: VL >10,000 copies/mL was commonly observed in women not on ART with CD4 cell counts >350 cells/µL, suggesting that CD4 cell counts may not be adequately sensitive in identifying women at greatest risk of MTCT. A large proportion of women entering ANC initiated ART before conception, and in this group more than 10% had VL>1000 copies/mL despite ART use. VL monitoring during pregnancy may help to identify pregnancies that require additional clinical attention to minimize MTCT risk and improve maternal and child health outcomes.
Keywords: South Africa; antiretroviral therapy; pregnancy; prevention of mother-to-child transmission; viral load.