Final answer:
Placenta previa, placental abruption, uterine rupture, and cervical incompetence are causes of third-trimester bleeding.
Step-by-step explanation:
The causes of third-trimester bleeding are placenta previa, placental abruption, uterine rupture, and cervical incompetence.
Placenta previa occurs when the placenta partially or completely covers the opening of the cervix. It is the leading cause of antepartum hemorrhage.
Placental abruption happens when the placenta separates from the uterus before delivery. It can result in vaginal bleeding and can be life-threatening for both the mother and the baby.
Uterine rupture is the tearing of the uterine wall during pregnancy. It is a rare but serious complication that can cause severe bleeding.
Cervical incompetence is when the cervix opens prematurely during pregnancy. This can lead to bleeding and preterm labor.