Threatened abortion: This is the most common cause of vaginal bleeding in early pregnancy, often due to implantation of the embryo or minor issues with the pregnancy that may resolve on their own. The presence of a positive pregnancy test along with bleeding points towards this diagnosis.

Miscarriage: Vaginal bleeding can be a sign of an impending or incomplete miscarriage. The positive pregnancy test confirms the pregnancy, and the bleeding suggests a potential issue with the viability of the pregnancy.
Ectopic pregnancy: Although less common, ectopic pregnancy is a significant concern with vaginal bleeding and a positive pregnancy test. It occurs when the embryo implants outside the uterus, often causing bleeding and abdominal pain.
Molar pregnancy: A rare condition where the placenta develops into an abnormal mass of cysts, it can cause vaginal bleeding and a positive pregnancy test due to the high levels of hCG produced.

Placenta previa: A condition where the placenta covers the cervix, which can cause severe vaginal bleeding. It's crucial to diagnose this condition to prevent severe maternal and fetal complications.
Placental abruption: This is a condition where the placenta separates from the uterus, causing bleeding and depriving the baby of oxygen and nutrients. It's a medical emergency that requires immediate attention.
Uterine rupture: Although rare, uterine rupture can occur, especially in women with a history of uterine surgery. It's a life-threatening condition that requires immediate surgical intervention.

Choriocarcinoma: A rare type of cancer that occurs in the uterus, often following a molar pregnancy, miscarriage, or ectopic pregnancy. It can cause vaginal bleeding and elevated hCG levels.
Pregnancy with a coexisting gynecologic malignancy: Rarely, vaginal bleeding in pregnancy can be due to a coexisting gynecologic cancer, such as cervical or endometrial cancer.