Which term describes painless vaginal bleeding in pregnancy?

The term that describes painless vaginal bleeding in pregnancy is placenta previa. This condition occurs when the placenta partially or completely covers the cervix, leading to bleeding as the pregnancy progresses, particularly in the third trimester. The bleeding is typically bright red and does not involve pain, which distinguishes it from other causes of bleeding during pregnancy, such as placental abruption or uterine atony.

In contrast, placental abruption often presents with painful bleeding due to the separation of the placenta from the uterine wall. Vasa previa, while also a concerning condition involving blood vessels near the cervix, typically presents with bleeding when membranes rupture and can be associated with fetal distress or complications. Uterine atony refers to a lack of muscle tone in the uterus leading to postpartum hemorrhage rather than bleeding during pregnancy. Thus, the hallmark characteristic of painless vaginal bleeding as associated with placenta previa makes it the correct choice in this context.