2017 Update on infectious disease
Four recent studies provide new data—with potential global impact—regarding birth defect rates in symptomatic and asymptomatic maternal Zika virus infection, dual-agent prophylaxis for postcesarean infection, tenofovir treatment of hepatitis B in pregnant women, and HIV transmission rates in patients receiving ART
IN THIS ARTICLE
Benefits of ART for reducing mother-to-baby HIV transmission outweigh higher risk of adverse outcomes
Fowler MG, Qin M, Fiscus SA, et al; IMPAACT 1077BF/1077FF PROMISE Study Team. Benefits and risks of antiretroviral therapy for perinatal HIV prevention. N Engl J Med. 2016;375(18):1726-1737.
Part of the larger PROMISE (Promoting Maternal and Infant Survival Everywhere) trial, a study by Fowler and colleagues compared the relative efficacy and safety of various proven ART strategies for prevention of mother-to-child transmission of HIV infection in women with relatively high CD4 counts.
Details of the study
The trial was conducted at 14 sites in 7 countries. Patients were stratified according to HBV coinfection status and country of origin. The primary efficacy outcome was frequency of early infant HIV infection.
,Women were randomly assigned to 1 of 3 treatment categories:
- zidovudine alone (zidovudine plus a single intrapartum dose of nevirapine, followed by 6 to 14 days of tenofovir plus emtricitabine postpartum)
- zidovudine-based ART (zidovudine in combination with lamivudine and lopinavir-ritonavir)
- tenofovir-based ART (tenofovir in combination with emtricitabine and lopinavir-ritonavir).
All regimens were continued through 6 to 14 days postpartum. All infants received nevirapine at birth and in the immediate postpartum period.
Two trial periods. During period 1 (April 2011-September 2012), safety data on tenofovir in pregnancy were limited. Women without HBV coinfection were assigned only to zidovudine alone or zidovudine-based ART. During period 2 (October 2012-October 2014), since more information about tenofovir use in pregnancy was available, the study protocol was modified to allow women to be assigned to any of the 3 regimens, regardless of their HBV status.
Inclusion criteria were as follows: CD4 count of at least 350 cells/mm3 (or country-specific threshold for initiating triple-drug ART, if that threshold was higher), gestation of at least 14 weeks and not in labor, no previous use of triple-drug ART, no clinical or immune-related indication for triple-drug ART, hemoglobin level of at least 6.5 g/dL, an absolute neutrophil count of at least 750 cells/mm3, an alanine aminotransferase level of less than 2.5 times the upper limit of normal range, an estimated creatinine clearance of greater than 60 mL/min, and no serious pregnancy complications. Patients were excluded if they had active tuberculosis, HBV infection requiring treatment, a structural or conduction heart defect, or a fetus with a serious congenital malformation.
Primary outcomes. The primary efficacy outcome was early infant HIV infection, defined as a positive infant HIV nucleic acid test result at birth or at 1 week postpartum. The primary safety outcome was a composite of adverse events.
Adverse events in mothers were defined as hematologic abnormalities, abnormal blood chemical values, or abnormal signs/symptoms during pregnancy through 1 week postpartum. Severe pregnancy composite outcomes were low birth weight (<2,500 g), preterm delivery before 37 weeks' gestation, spontaneous abortion (<20 weeks), stillbirth (≥20 weeks), or congenital anomaly. Adverse events in infants were defined as death from any cause, hematologic abnormalities or abnormal blood chemical values, and abnormal signs/symptoms through 1 week postpartum.
A total of 3,490 mother-infant sets were included in the analysis (2,261 during trial period 1 and 1,229 during trial period 2). Baseline maternal characteristics were well balanced between groups. Most women were African, young (median age, 26 years), and asymptomatic.
Related article:
2016 Update on infectious disease
Study results
The combined maternal ART-treated groups had significantly lower rates of early transmission of HIV infection compared with the zidovudine-alone group (0.5% vs 1.8%, -1.3 percentage points; CI, -2.1 to -0.4). The zidovudine-based ART-treated group had a significantly higher rate of infant HIV-free survival through postpartum week 1 than did the zidovudine-alone group (P = .001) or the tenofovir-based ART group (P = .002).
When examining trial periods 1 and 2 combined, the zidovudine-based ART group experienced significantly higher rates of any adverse event than those receiving zidovudine alone (21.1% vs 17.3%, P = .008) and higher rates of abnormal blood chemical values (5.8% vs 1.3%, P<.001). During period 2 alone, the tenofovir-based ART group had significantly higher rates of abnormal blood chemical values than did the zidovudine-alone group (2.9% vs 0.8%, P = .03). There were no significant differences between the 2 ART treatment groups. No maternal deaths occurred during the study, and the trial-drug discontinuation rate was low (2%-5%) and did not vary among the 3 groups.
During trial periods 1 and 2, the zidovudine-based ART group had significantly higher rates of adverse pregnancy outcomes than did the zidovudine-alone group (40% vs 27.5%, P<.001). These included low birth weight less than 2,500 g (23% vs 12%) and preterm delivery before 37 weeks (20.5% vs 13.1%). During trial period 2, the tenofovir-based ART group had significantly higher rates of adverse pregnancy outcomes than did the zidovudine-alone group (34.7% vs 27.2%, P = .04). There were no significant differences for any outcome between the 2 ART-treated groups, and there were no significant differences in stillbirth or spontaneous abortion and congenital anomalies among the 3 groups.
Regarding severe pregnancy outcomes, there were no significant differences (composite or individual) between the zidovudine-based ART group and the zidovudine-alone group. The tenofovir-based ART group experienced significantly higher rates of composite severe adverse pregnancy outcomes compared with the zidovudine-based ART group (9.2% vs 4.3%, P = .02), and very preterm birth before 34 weeks (6.0% vs 2.6%, P = .04).
Infant safety outcomes were also examined. There were no significant differences for composite or individual adverse neonatal outcomes other than death. The tenofovir-based ART group experienced a significantly higher rate of infant death than did the zidovudine-based ART group (4.4% vs 0.6%, P<.001). However, a post hoc analysis suggested that extreme prematurity contributed to the infant mortality.
Limitations of the study
This study had minor limitations. It divided patients into only 2 major categories with respect to gestational age--more than or less than 34 weeks. Some maternal medical conditions, such as malaria, were not controlled for. In addition, breastfeeding and formula feeding were combined for analysis, and we know that breastfeeding would inherently confer a higher risk of HIV transmission.
Nevertheless, this study was thoughtfully designed and carefully conducted, and the results are of significant global impact.
Although antenatal ART was associated with a higher risk of adverse maternal and neonatal outcomes when compared with zidovudine alone, these risks are outweighed by the benefit of significantly lower rates of early HIV transmission. Therefore, women who meet the World Health Organization's (WHO) eligibility criteria should be treated with combination ART during pregnancy. The WHO major eligibility criteria for ART during pregnancy are:
- CD4 count of ≤350 cells/mm3, irrespective of clinical staging
- clinical stage 3 or stage 4 disease, irrespective of CD4 cell count.
The WHO recommends starting ART at 14 weeks' gestation.8
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