Brief Report: Viral Load Monitoring in Pregnancy to Predict Peripartum Viremia in South Africa.

Introduction: Enhanced postnatal prophylaxis is recommended in infants of women with viremia during labor, as identified by viral load (VL) testing late in pregnancy. However, data on the use of antenatal VL to predict peripartum viremia are few, particularly in women starting antiretroviral therapy (ART) in pregnancy who experience initial VL declines.

Methods: Between January 2016 and August 2017, we identified HIV-infected women who initiated ART (tenofovir, emtricitabine, and efavirenz) antenatally and had a VL <400 copies/mL before delivery in Cape Town, South Africa. VLs were repeated postdelivery, and sensitivity, specificity, and positive and negative likelihood ratios (LR+ and LR-) for antenatal VL <100 copies/mL in predicting peripartum VLs <100 and <400 copies/mL were calculated.

Results: Among 322 women (median age 29 years, 44% with a history of ART use, median gestation of antenatal VL 33 weeks), antenatal VL was <100 copies/mL in 89% and 100-400 copies/mL in 11%. At a median 9 days postpartum, 91%, 7%, and 2% of women had a VL <100, 100-400, and >400 copies/mL, respectively. Sensitivity of antenatal VL <100 copies/mL in predicting peripartum VL <100 copies/mL was 0.95 (95% confidence interval: 0.92 to 0.97), and specificity was 0.71 (95% confidence interval: 0.51 to 0.87; LR+ 3.28, LR- 0.07). Performance was slightly weaker to detect peripartum VL <400 copies/mL but was similar across strata of gestation at antenatal VL and history of ART use.

Discussion: Antenatal VL is a useful predictor of peripartum viremia in women who started ART in pregnancy and attained a VL <400 copies/mL antenatally and may be used to target enhanced postnatal prophylaxis interventions.