BACKGROUND: High rates of liver enzyme elevation (LEE) in women receiving antiretroviral treatment (ART) during pregnancy have been reported but causes remain unclear. We estimated the prevalence and risk factors of LEE in a national prospective multicenter cohort. METHODS: We studied 5748 pregnant women living with HIV enrolled in the French Perinatal Cohort 2005-2014, treated with ART, with no active hepatitis B or C co-infection. Adjusted hazard ratio (aHR) were estimated using Cox models with ART as time-dependent variable, separately for women on ART at conception and those initiating ART during pregnancy. RESULTS: LEE (grade>1) was observed in 16.7%, grade 3-4 in 2%. Among women with LEE, 6.7% had preeclampsia, 9.8% intrahepatic cholestasis of pregnancy, and 1.4% other identified medical causes. Most LEE (82.2%) were unexplained. In women with unexplained LEE, LEE was the reason for hospitalization in 51 (6%) women, cesarean section in 13 (2%), induction of labour in 3 (0.4%), and change in ART regimen in 49 (6%) women. Unexplained LEE was associated with higher risk of preterm births, p<0.001.Among women on ART at conception, the risk of unexplained LEE was lower with NNRTI-based regimens than with PI-based regimens: aHR=0.5[0.3-0.7], with no difference among the PI drugs. Most women initiating ART during pregnancy were on a PI-based regimen (89%). Among them, LEE was less frequent for women on nelfinavir vs. lopinavir/r (aHR=0.4[0.2-0.8]). CONCLUSION: Rates of LEE among pregnant women living with HIV are high and impact obstetrical care management. The possible role of PIs needs further investigation.