Hepatitis E virus (HEV) infection may occur in pregnant women who had chronic hepatitis B virus (HBV) infection. This study aimed to evaluate whether HEV-HBV co-infection increases the risk of obstetric complications and perinatal adverse outcomes in pregnant women. We investigated the clinical data of 3,251 pregnant women with chronic HBV infection. The obstetric complications and perinatal adverse outcomes were compared between patients with HEV-HBV co-infection and patients who had pure chronic HBV infection. Of the 3,251 pregnant women with chronic HBV infection, 98 patients (3%) had HEV-HBV co-infection. Compared with healthy controls, there is an increased risk of obstetric complications in pregnant women with pure HEV infection [odds ratio (OR)= 3.99, p < 0.001], pure chronic HBV infection (OR = 2.76, p < 0.001), and HEV-HBV co-infection (OR = 5.41,p < 0.001). The rate of obstetric complications and perinatal adverse outcomes is significantly higher in pregnant women with HEV-HBV co-infection compared with those with pure chronic HBV infection or those with pure HEV infection (all p< 0.05). The HEV-HBV co-infection is the most significant risk factor for perinatal adverse outcomes (OR = 15.47, p < 0.001), followed by pure HEV infection (OR = 10.22, p < 0.001), and pure HBV infection (OR = 5.82, p < 0.001). HEV infection increases the risk of obstetric complications and perinatal adverse outcomes in pregnant women with chronic HBV infection.