364. Association of Maternal ARV Use with Microcephaly in HIV-Exposed Uninfected Children

BACKGROUND: Perinatal HIV transmission has dramatically decreased with combination antiretroviral (ARV) regimens, but complications among HIV-exposed uninfected (HEU) children, such as microcephaly, warrant ongoing surveillance. METHODS: We evaluated HEU children enrolled in the Surveillance Monitoring for ART Toxicities (SMARTT) study, a prospective cohort study conducted by the PHACS network at 22 US sites. Microcephaly was defined using 2000 CDC Growth z-scores for head circumference (HC) measured at 6–36 months of age (z-score <−2) and using Nellhaus standards (<2nd percentile) after age 3 (“SMARTT” criteria), or using Nellhaus standards across all ages. Modified Poisson regression models were fit to obtain relative risks (RRs) for associations between in utero ARV exposure and microcephaly status, adjusted for potential confounders. Sensitivity analyses were conducted. Neurodevelopmental functioning was compared between HEU children with vs. without microcephaly. RESULTS: Among 3055 SMARTT participants enrolled as of April 2017 with a HC measurement over 5.1 years median follow-up (IQR = 3.0, 7.2), 159 (5.2%, 95% CI: 4.4–6.1%) had microcephaly identified by Nellhaus criteria and 70 (2.3%, 95% CI: 1.8–2.9%) by SMARTT criteria. In adjusted models, in utero exposure to efavirenz (4.7% exposed) was associated with increased risk of microcephaly by both Nellhaus standards (aRR=2.02, 95% CI: 1.16, 3.51) and SMARTT criteria (adjusted RR = 2.56, 95% CI: 1.22, 5.37). These associations were more pronounced among children exposed to combination regimens of efavirenz which included zidovudine+lamivudine than those including tenofovir+emtricitabine (Figure 1). Associations of microcephaly with efavirenz persisted in several sensitivity analyses (Figure 2). Protective associations were observed for darunavir exposure (aRR = 0.50; 95% CI: 0.24, 1.00). HEU children with microcephaly had lower mean scores on neurodevelopmental assessments at ages 1 and 5 years and higher prevalence of impairment than those without microcephaly. CONCLUSION: Efavirenz exposure during pregnancy was associated with a higher risk of microcephaly in infancy and childhood. These findings may support identification of alternatives to efavirenz as part of first-line ARV therapy. [Image: see text] [Image: see text] DISCLOSURES: All authors: No reported disclosures.