Viral load rebounds in a third of women who start HIV therapy during pregnancy or postpartum, South African study shows

Approximately one-third of HIV-positive women who attain viral suppression after starting antiretroviral therapy (ART) during pregnancy experience a significant rebound in viral load in the year after giving birth, according to results of a South African study published in Clinical Infectious Diseases. 

“The key findings are that up to one-third of women who achieve initial viral suppression experience viremia within one year postpartum, and that most of these women experience VL [viral load] > 1000 copies/mL, often with repeated episodes over time,” comment the investigators. “The high incidence of viremia on ART in routine care documented here is of clear concern and has significant implications for the population-level impact of policies for universal ART.”

In low- and middle-income countries, the World Health Organization Option B+ strategy calls for universal, lifelong ART for all HIV-positive pregnant women, regardless of CD4 count. The numbers of HIV-positive pregnant or postpartum women starting ART has increased three-fold in the past five years.

There are concerns about adherence to ART among pregnant and postpartum women. Several studies have demonstrated significant levels of disengagement from HIV care among postpartum women. However, data concerning viral load control among women who started HIV treatment during pregnancy are limited.

An international team of investigators therefore designed a study to examine patterns of viral control in pregnant and postpartum women who started ART during pregnancy and used routine health services in Cape Town, South Africa.

The 523 women included in the analysis were enrolled in the prospective MCH-ART cohort. Viral load was monitored separately from routine clinic visits. Viral suppression was defined as maintenance of a viral load below 50 copies/ml; a minor viraemia was viral load between 50 and 1000 copies/ml and major viraemia was a viral load above 1000 copies/ml.

The participants had a median age of 28 years. On average ART was started during the 21st week of pregnancy. A quarter of the cohort had taken a previous short course of antiretrovirals for the prevention of mother-to-child transmission and 3% had stopped taking a previous course of ART. Median CD4 count and viral load at the point of ART initiation were 345 cells/mm³ and 8000 copies/ml, respectively.

After initial viral suppression, the participants contributed a total of 5092 women-months of follow-up; 86% of this observation was postpartum. The median number of post-suppression viral load tests was five per person.

Overall, 70% of women maintained viral suppression throughout the follow-up period, with 8% having a minor rebound in viral load and 22% experiencing major viraemia. The majority of women with major viraemia had two or more viral load measurements above 1000 copies/ml.

The proportion of women with elevated viral load measures increased steadily with time after initial viral suppression. Cumulatively, one year after giving birth, 37% of women in the study had had at least one viral load above 1000 copies/ml. Median peak viral load was approximately 6500 copies/ml, close to the pre-therapy viral load peak.

Factors associated with higher incidence of major increases in viral load were younger age (18 to 22 years vs 34 years and older, IRR = 3.67; 95% CI 1.78-7.56), starting ART during third trimester (vs first trimester, IRR = 2.21; 95% CI 1.13-4.34), stopping a previous ART regimen (IRR = 2.94; 95% CI 12.9-6.69) and postpartum follow-up (vs antenatal follow-up, IRR = 6.40; 95% CI 1.54-26.69). Analysis restricted to the postpartum period showed that each additional month of follow-up was associated with an 11% increase in the incidence of viraemia (IRR = 1.11; 95% CI 1.07-1.15).

The authors note that the incidence of viral breakthrough observed in their study is similar to that seen in studies conducted in richer settings.

“The parallels across countries in findings of high levels of viraemia in HIV-infected women during the postpartum period despite ART are striking, and may point to cross-cutting psychological, social and/or behavioral drivers of ART non-adherence during this phase of women’s lives,” suggest the authors. “Understanding why levels of viraemia on ART appear so consistent across settings in this patient population remains a critical question for optimizing treatment programmes globally.”