The objective of this study is to investigate the expression of autophagy-related proteins (LC3 and beclin-1) in human placentas and the changes they undergo in the placentas from pregnancies complicated by preeclampsia (PE) and to explore the regulatory mechanisms of these proteins in JEG-3 cells in response to hypoxia or cytokine treatment. The presence of autophagosomes was confirmed with electron microscopy and the expression of LC3 and beclin-1 by immunoimaging methods in human placental trophoblasts. Compared with the placentas from normal pregnancies, the expression of LC3-II protein, but not beclin-1, was increased in the placentas from severe PE. In JEG-3 cells, hypoxia (O₂ < 1%) induced a modest but not significant increase in the expression of LC3-II with a significant decrease in the expression of beclin-1. Meanwhile, TNF-α treatment induced a significant increase in the expression of LC3-II without a significant change in the expression of beclin-1. Our data suggests that increased autophagic activity in the placenta may be implicated in the pathophysiology of PE.