Threatened miscarriage refers to the occurrence of symptoms suggesting a possible miscarriage, such as severe abdominal pain or vaginal bleeding. However, a threatened miscarriage does not always progress to an actual miscarriage. With appropriate treatment and oral medication, the majority of embryos can be saved during a threatened miscarriage. If the quality of the embryo is poor and the symptoms of threatened miscarriage continue to worsen, it may develop into a natural miscarriage. However, there is no specific clinical guideline on how many days it may take for a natural miscarriage to occur following a threatened miscarriage. If the symptoms of threatened miscarriage are mild, with only slight abdominal pain or vaginal bleeding, it may not lead to a natural miscarriage, or it might take up to a week to occur naturally. If the symptoms of threatened miscarriage are severe, featuring intense abdominal pain or heavy vaginal bleeding, it generally may result in a natural miscarriage within one to two days.