Threatened abortion or miscarriage: This is the most common cause of vaginal bleeding in early pregnancy, especially if the bleeding is painful. It occurs when there is a risk of miscarriage but the cervix is still closed.

Placenta previa: A condition where the placenta partially or completely covers the cervix, leading to painless vaginal bleeding, typically in the second or third trimester.
Placental abruption: A condition where the placenta separates from the uterus, causing painful vaginal bleeding and potentially compromising fetal health.
Ectopic pregnancy: A pregnancy that develops outside the uterus, often presenting with painful vaginal bleeding and abdominal pain.

Uterine rupture: A life-threatening condition where the uterus tears, often causing severe abdominal pain and vaginal bleeding. This is more common in women with a history of uterine surgery, including cesarean deliveries.
Molar pregnancy: A rare condition where a non-viable fertilized egg implants in the uterus, leading to abnormal growth and potentially causing vaginal bleeding.
Vaginal or cervical trauma: Any injury to the vagina or cervix can cause bleeding, which may be painful depending on the severity and location of the trauma.

Vasa previa: A condition where fetal blood vessels are present in the membranes covering the cervix, at risk of rupture and severe fetal hemorrhage, typically presenting with painless vaginal bleeding.
Uterine artery pseudoaneurysm: A rare condition that can cause vaginal bleeding due to a false aneurysm of the uterine artery, potentially life-threatening if not recognized and treated.
Choriocarcinoma: A rare type of cancer that can develop in the uterus during pregnancy, causing abnormal vaginal bleeding among other symptoms.