Final answer:
The primary difference between the symptoms of placenta previa and abruptio placentae is the presence of bleeding.
Step-by-step explanation:
The primary difference between the symptoms of placenta previa and abruptio placentae is the presence of bleeding. Placenta previa is a condition in which the placenta partially or completely covers the opening of the cervix, leading to profuse vaginal bleeding after week 24 of pregnancy. On the other hand, abruptio placentae is a condition in which the placenta separates from the uterine wall prematurely, causing bleeding between the placenta and the uterine wall.