목적: Premature rupture of membrane (PROM) is a serious obstetric disease causing morbidity and mortality to mother and fetus. Although the cause of PROM is not clearly defined, the ruptured membrane is naturally healed in cases up to 5%. We have demonstrated the natural healing of pored amniotic membrane using our in vitro tissue culture system. In this study, we aimed to investigate whether the healing process of the pored membrane is different according to the pore size. 방법: Amniotic membrane was peeled off from the human placenta and IHC stained. The amnion tissues were cultured in vitro. The amniotic epithelial stem cells cultured from amniotic membrane were characterized. In our pore culture model, the amnion tissues punched with biopsy punch of 8 mm were re-punched with biopsy puch of 1 mm, 2 mm and 3 mm for making different pore sizes in 12-well culture dish. The tissues were cultured in 37℃and 5% CO2, and media was changed every other day. The pore size was periodically calculated to quantify the healing process until the pores were closed. 결과: Amniotic membrane was positive for stem cell markers (SSEA-4, TRA 1-60, and OCT-3/4) by IF staining. And cells extracted from amniotic membrane also had positive expression of stem cell markers. The pore size in APCT model was time-dependently healed according to the pore size. The pore sizes in all three groups,1 mm (n=24), 2 mm (n=21), and 3 mm (n=18), were significantly reduced 10 days after poring compared with the starting day of culture. At the 22nd day, the pore size of 1 mm group was decreased to 30% and the pore sizes of 2 mm and 3 mm groups were decreased to 56% and 66.5%. 결론: The pore of amniotic membrane was recovered spontaneously in a certain period of time and the duration of completion of healing was dependent on the size of pore. Larger pores requires longer time to be healed. Based on our data, we could hypothesize that a stemness of amnion- derived cells has a important role for the natural healing of pored amniotic membrane.