Cervical ectropion or cervical polyp: This condition is a common cause of vaginal spotting in the second trimester due to the increased blood flow and softening of the cervix during pregnancy. The spotting is usually light and intermittent.

Placenta previa: Although more commonly associated with painless vaginal bleeding in the third trimester, placenta previa can occasionally cause spotting in the second trimester, especially if there is a partial placenta previa.
Marginal placental abruption: This condition involves the placenta separating from the uterus at the edge, which can cause vaginal bleeding or spotting. It might be accompanied by mild abdominal pain.
Sexual intercourse: Vaginal spotting after sexual intercourse can occur due to the increased blood flow to the cervix and vagina during pregnancy, making these areas more susceptible to minor trauma.

Placental abruption: A more significant separation of the placenta from the uterus can cause severe vaginal bleeding and abdominal pain. It is crucial to identify this condition promptly due to its potential to compromise both maternal and fetal health severely.
Uterine rupture: Although rare, uterine rupture is a life-threatening emergency that can cause vaginal bleeding, severe abdominal pain, and fetal distress. It is more common in women with a previous uterine scar (e.g., from a cesarean section).
Vasa previa: This condition involves fetal blood vessels crossing the internal cervical os, which can cause painless vaginal bleeding when these vessels rupture. It is critical to diagnose vasa previa because it can lead to severe fetal hemorrhage.

Choriocarcinoma: A rare type of gestational trophoblastic disease that can cause vaginal bleeding during pregnancy. It is more commonly associated with a molar pregnancy but can occur with a normal pregnancy as well.
Uterine arteriovenous malformation (AVM): A rare vascular anomaly that can cause vaginal bleeding during pregnancy due to the risk of rupture of the AVM.