This large multi-center, retrospective cohort study of 612 pregnant and non-pregnant women on NVP and non-NVP ART regimens assessed the cumulative incidence of hepatic and rash-related adverse events over the first 18 weeks post-ART initiation. The strengths of this study include the multi-center nature of the study, the significant sample size and the use of a large non-pregnant comparison group, a group that has been missing from other studies evaluating the relationship of AEs and ART during pregnancy. The majority of liver and skin AEs in both regimen groups in the current study occurred within 6 weeks of initiating ART. There were no significant differences in the overall percentage of patients developing LEE between regimen groups. We did not find a statistically significant association between baseline CD4 cell count above 250 cells/mm3 and the risk of hepatotoxicity in patients taking NVP in univariate and multivariate analyses. Though a non-significant trend towards an increased risk of LEE in the higher CD4 count group was noted in the univariate analysis, no such association was noted in the multivariate analysis. NVP use in women with baseline CD4 counts ≤250 cells/mm3, including pregnant women, resulted in a hepatic safety profile similar to women treated with non-NVP regimens.
In comparison, both pregnant and non-pregnant women on NVP with a baseline CD4 count >250 cells/mm3 had a significantly increased rate of grade ≥2 rash compared to women on non-NVP regimens with CD4 count >250 cells/mm3. NVP use was predictive of rash when controlling for CD4 count at regimen initiation and pregnancy.
The lack of association of an effect of CD4 count on LEE is consistent with recent studies 
. Ouyang reported on 1358 women with ART exposure during pregnancy and found no association between CD4 cell count above 250 cells/mm3
and risk of hepatotoxicity in patients taking NVP 
. Our findings are also consistent with a large review on NVP and hepatotoxicity which also failed to demonstrate an association 
. However, the results from this study are in contrast to prior published studies in which a greater proportion of women on NVP with CD4 counts >250 cells/mm3
had moderate to severe side effects as compared to those with CD4 counts ≤250 cells/mm3 
. Bersoff-Matcha found that both a higher CD4 at initiation of NVP therapy and a higher nadir CD4 count were strongly associated with the development of severe rash and discontinuation of therapy 
. The risk of NVP–induced hepatitis was found to be increased 12-fold in women with greater than 250 CD4 cells/mm3 
. In a summary analysis of 17 clinical trials using NVP, the risk ratio was 9.8 in women with rash-associated hepatic events with CD4 count >250 cells/mm3
as compared to those with lower CD4 counts. 
In this study, pregnancy was not an independent risk factor for the development of LEE or rash. In contrast, a recent study of 2050 HIV-infected pregnant women concluded that NVP was not significantly associated with risk of LEE, and that pregnancy was a risk factor for LEE 
Hepatitis C co-infection was independently associated with the development of LEE in this cohort. This finding is consistent with previous studies that have examined the association of HCV with hepatoxicity in patients on ART. Co-infected patients in these studies were found to have a significantly greater risk of experiencing hepatic events 
. Vogel and colleagues studied the impact of chronic viral hepatitis on the pharmacokinetics of NVP. They found that other factors such as accumulating NVP drug levels may be responsible for an increased risk of liver damage in HIV/HCV co- infected patients 
. Rivero and colleagues found that HCV co-infection increased by two to seven fold the risk of developing LEE >2 in patients treated with non-nucleoside reverse transcriptase inhibitors 
. Bonnett showed that patients with HCV and/or HBV co-infection who received NVP containing regimens had a 45% increase in hepatotoxicity at month 12 of follow-up when compared to patients without co-infection 
In our study, NVP use was predictive of rash even when controlling for CD4 and pregnancy. The 2NN Trial reported grade ≥3 rash occurrence in 3.4% of patients taking NVP twice daily 
. Aggregate data from 1,752 patients who participated in 33 NVP clinical trials revealed a rash rate of 17.0%, the majority of which occurred within 6 weeks of NVP initiation: 6.0% discontinued NVP due to rash, and 0.5% developed Steven-Johnson syndrome 
. Pollard reviewed prospective clinical trials with NVP and found an incidence of 0.3% SJS 
Recent studies have demonstrated that virologically suppressed patients switching to NVP do not show a higher risk of hepatotoxicity or rash dependent on CD4 counts 
. The ATHENA cohort also suggested that the incidence of hypersensitivity reaction associated with NVP in patients with undetectable HIV RNA load at the start of NVP is lower in patients with prior treatment experience than those who are treatment naïve. While the importance of VL as a predictor for rash with NVP remains debatable, the current study has demonstrated that patients on non-NVP regimes had a significant increase in liver enzyme elevations at baseline HIV-1 RNA VL >100,000 copies/µl, a finding that was not seen in subjects on NVP-containing regimens (p
During pregnancy there is a lowering of absolute CD4 count due to hemo-dilution. The stability of CD4 percentage measurements in comparison to absolute CD4 counts between prepartum and postpartum periods have been confirmed 
. Similar to absolute CD4 count, CD4 >20% in this study demonstrated a non-significant trend in the increase of LEE and rash-related events associated with the use of NVP.
Our study has limitations that should be considered. There was an overrepresentation of pregnant women who were using NVP, had higher CD4 counts, and were of younger age. These women were also less likely to have Hepatitis C. It could be hypothesized that the reason why LEE and rash were seen more frequently in women with higher baseline CD4 counts on NVP-based regimens was due to these confounding factors. However, pregnancy was not an independent predictor of LEE or rash. Since women in the United States who are HIV-infected and pregnant are many times diagnosed earlier in their disease process during pregnancy through HIV screening programs, and are younger due to the childbearing years, this overrepresentation is hard to avoid 
The limitation of a retrospective study resulted in the reliance on chart documentation to distinguish drug induced hepatotoxicity from hepatotoxicity due to other causes. Women who are pregnant have an increased rate of LEE due to conditions that are unique to pregnancy 
. In addition due to insufficient reporting in clinic records, alcohol use, drug use, and Hepatitis B were not evaluated as confounding factors. The fact that a positive hepatitis serologic result was used as a surrogate for chronic active HCV infection may have resulted in an attenuation of the association between HCV and LEE as several of the women who were HCV antibody positive may have cleared their infection. Finally, AST/ALT values may not be specific enough markers for liver injury. It is known that only a small proportion of those with LEE will eventually develop fulminant hepatitis or acute liver failure and that LEE often resolve without any intervention. Many instances of drug induced liver disease are unpredictable and asymptomatic.
The results from this study should be considered in assessing the recommendations for use of NVP in all women, but particularly for women of childbearing age in resource limited settings (RLS). The 2009 World Health Organization (WHO) now recommends starting lifelong ART for all pregnant women with a CD4 count at or below 350 cells/mm3
regardless of symptoms. ART is recommended to be continued in all pregnant women during the breastfeeding period to reduce the risk of HIV transmission. These guideline changes mean that more pregnant women will be initiating NVP-based regimens as part of first-line ART therapy in RLS 
. In comparison to other studies in RLS where an association between high CD4 counts and LEE and rash have been reported, this study supports increased confidence on the use of NVP in similar populations as pregnancy status, NVP use, and baseline CD4 count ≥250 cells/mm3
were not independent predictors for the development of LEE 
. In addition, the DART study showed that routine laboratory monitoring for toxic effects in HIV patients receiving ART had no benefit in RLS 
. Our study confirms that while clinical monitoring would detect the increased risk of rash seen with NVP use in women with higher CD4 cell counts, the risk of LEEs described may not result in significant hepatotoxicity to necessitate lab testing. As rash and hepatic events occurred more frequently in the first 6 weeks of NVP initiation in this analysis, more diligent clinical monitoring is recommended during this time frame.
Our study cohort is representative of the HIV epidemic in women in U.S. women in terms of age, race, HIV transmission risk and HCV status, and therefore contributes to the knowledge needed to better characterize adverse events specific to this population (7). This large cohort study provides additional information for clinicians in assessing the risk of NVP-induced liver and skin toxicity by taking into account the short latency period and potential risk factors such as baseline CD4 counts and HCV co-infection. All HCV co-infected women on NVP based regimens should undergo close monitoring for LEE. Empiric use of NVP in the absence of resources to determine baseline CD4 count and monitor liver enzyme levels continues to call for careful consideration of the risks and benefits of NVP therapy. However, with the significant increase in women of childbearing age initiating NVP-based ART in RLS, where there is limited laboratory capacity to monitor for LEE, this study provides supportive evidence for the use of NVP in this population.