Factors Associated with MTCT of HIV Despite Optimal Conditions
The rate of MTCT of HIV-1 among mothers who delivered in the French Perinatal Cohort between 1997 and 2006 was 1.5%. Even when optimal conditions were met-- meaning a term delivery of 37 weeks or more to a mother receiving antiretroviral therapy (ART), with the last maternal viral load at or prior to delivery being <500 copies/ml, and no evidence of breast-feeding—there were instances where “residual transmission” occurred. In fact, 20% of the infected children born during the study period were infected despite achievement of these optimal conditions. This study, which compared children born under these optimal conditions who were infected with HIV to children born under similar conditions who were not infected with HIV, sought to better investigate factors which may explain why, despite the achievement of optimal conditions, some children were still infected with HIV.
Among 7425 mother-infant pairs in the French Perinatal Cohort from 1997-2006, 19 children (termed “cases”) were infected under the aforementioned optimal conditions. The women who birthed these 19 children were compared to women birthing 60 non-infected children (termed “controls”) born under similar conditions. The cases and controls had similar rates of pregnancy complications, gestational age at initiation of care, gestational age of delivery, drug/alcohol use during pregnancy, premature rupture of membranes, and route of delivery (47% and 48% of women in each group were delivered via elective cesarean sections, respectively). The cases and controls also had similar rates of women diagnosed with HIV-1 infection prior to pregnancy, as well as similar rates of AIDS.
With respect to ART, HIV-1 RNA levels, and CD4 T-cell counts, cases and controls used similar first ART regimens in pregnancy, and the type of ART used at delivery was similar in both groups. Cases and controls both had similar rates of intrapartum prophylaxis (100% and 98.3%), single-dose nevirapine (5% in both groups), and had similar types of postnatal prophylaxis for infants. Maternal CD4 counts did not appear to be different between case patients and control subjects.
Notable differences in these areas between the two groups were also observed. Case patients received ART prior to conception less frequently than controls, reported problems with ART adherence during pregnancy more often, and had median peak viral loads during pregnancy which were significantly higher for cases in comparison with controls. For example, no case patients had a peak viral load of <500 copies/ml, in comparison to 40% of control patients. Sixty-three percent of case patients had peak viral loads of >10,000 copies/ml, compared to 36% of control patients. Fewer case patients also had viral loads of <50 copies/ml near delivery than control patients. Overall, the viral load was initially higher and decreased more slowly in case patients than in control patients. These differences between case and control patients were statistically significant at 14, 28, and 32 weeks. When analyses were performed which controlled for the other factors related to MTCT, mothers with a plasma HIV-1 viral load of >500 copies/ml at 30+ 4 weeks were approximately 23 times as likely to transmit HIV-1 to their child as women with viral loads <500 copies/ml.
This article represents a worthwhile contribution to the existing literature because the authors attempt to identify risk factors for MTCT of HIV-1 even when optimal conditions are met. One potential shortcoming of this article was the cutpoint for the viral load, which was <500 copies/ml. The goal for most providers at this time is the achievement of an undetectable viral load. Given that this is a historical cohort, and that at the time the technological capability did not exist in most laboratories to test for a viral load <50 copies/ml, and because retesting at this time the blood specimens collected during the study using a lower threshold is not possible, this is an understandable limitation. The small size of the number of cases and the retrospective nature of the study are additional recognizable study limitations which may limit the strength of the findings. The overall conclusion of the study, however rings true, and suggests that early and sustained control of viral load is associated with a decreasing risk of MTCT in patients for whom optimal conditions have been met. It is important to incorporate these findings when attempting to determine the ideal timing for initiation of ARV during pregnancy.
--Summarized by Barrett Robinson, MD, MPH
Barrett Robinson is a Maternal-Fetal Medicine Fellow at Northwestern Memorial Hospital, where he participates in the ongoing care of one of Illinois’ largest clinics exclusively servicing HIV-positive pregnant patients.
Citation:
Tubiana R, et al. Factors associated with mother to child transmission of HIV-1 despite a maternal viral load <500 copies/ml at delivery: a case-control study nested in the french perinatal cohort (EPF-ANRS CO1). Clin Infect Dis. 2010 Feb 15;50(4):585-96.
Original Article (Subscription may be required)
Abstract
Citation:
Tubiana R, et al. Factors associated with mother to child transmission of HIV-1 despite a maternal viral load <500 copies/ml at delivery: a case-control study nested in the french perinatal cohort (EPF-ANRS CO1). Clin Infect Dis. 2010 Feb 15;50(4):585-96.
Original Article (Subscription may be required)
Abstract
