Objective:
The objective of this study is to assess whether pregnancy is associated with an increased risk of liver enzyme elevation (LEE) and severe LEE in HIV-positive women on antiretroviral therapy (ART).

Design:
Two observational studies: the UK Collaborative HIV Cohort (UK CHIC) study and the UK and Ireland National Study of HIV in Pregnancy and Childhood (NSHPC).

Methods:
Combined data from UK CHIC and NSHPC were used to identify factors associated with LEE (grade 1–4) and severe LEE (grade 3–4). Women starting ART in 2000–2012 were included irrespective of pregnancy status. Cox proportional hazards were used to assess fixed and time-dependent covariates including pregnancy status, CD4+ cell count, drug regimen and hepatitis B virus/hepatitis C virus (HBV/HCV) coinfection.

Results:
One-quarter (25.7%, 982/3815) of women were pregnant during follow-up, 14.2% (n = 541) when starting ART. The rate of LEE was 14.5/100 person-years in and 6.0/100 person-years outside of pregnancy. The rate of severe LEE was 3.9/100 person-years in and 0.6/100 person-years outside of pregnancy. The risk of LEE and severe LEE was increased during pregnancy [LEE: adjusted hazard ratio (aHR) 1.66 (1.31–2.09); severe LEE: aHR 3.57 (2.30–5.54)], including in secondary analyses excluding 541 women pregnant when starting ART. Other factors associated with LEE and severe LEE included lower CD4+ cell count (<250 cells/μl), HBV/HCV coinfection and calendar year.

Conclusion:
Although few women developed severe LEE, this study provides further evidence that pregnancy is associated with an increased risk of LEE and severe LEE, reinforcing the need for regular monitoring of liver biomarkers during pregnancy.