Which pair of causes each accounts for approximately one-third of APH cases in the lecture?

The lecture identifies **placenta praevia** and **abruptio placentae** as each accounting for approximately one-third of APH. Other listed causes include vasa praevia, local cervical or vaginal causes, excessive show, trauma, and infection, but they are not the pair specified as each contributing about one-third.\n\n**Key takeaway:** Praevia and abruption are the two principal placental causes highlighted.\n\n**Glossary:** **Placenta praevia**: Placental implantation wholly or partly in the lower uterine segment; **abruptio placentae**: Premature separation of a normally situated placenta.