AimsTo investigate the impact of pregnancy with combined hepatitis B virus (HBV) infection and Gestational diabetes mellitus (GDM) on fetal growth and adverse perinatal outcomes. MethodsAll the pregnant women with HBV infection and/or GDM who delivered at Women’s Hospital, Zhejiang University between January 2015, and September 2022 were included. A total of 1633 pregnant women were recruited in the final analysis, including 409 women with HBV infection and GDM, 396 with HBV infection only, 430 with GDM only, and 398 without HBV infection and GDM. Linear and logistic regression models were used to study the impact of pregnancy with combined HBV infection and GDM on fetal growth and adverse perinatal outcomes. ResultsPregnancy with combined HBV infection and GDM was associated with increased Z-scores on primary fetal ultrasound parameters and significantly increased the risk of fetal femur length overgrowth (OR: 2.88, 95 % CI: 1.13 ∼ 7.35), placental abruption (OR: 3.64, 95 % CI: 1.18 ∼ 11.22), and macrosomia (OR: 4.19, 95 % CI: 1.66 ∼ 10.56) compared to pregnancy without HBV infection and GDM. ConclusionsBoth maternal HBV infection and GDM are independently associated with adverse perinatal outcomes. Their combination further increases the risk of adverse perinatal outcomes.