Placental abruption is most likely to occur in the last trimester of pregnancy, especially in the last few weeks before birth. Signs and symptoms of placental abruption include: 
Vaginal bleeding, although there might not be any
Abdominal pain
Back pain
Uterine tenderness or rigidity
Uterine contractions, often coming one right after another
 Abdominal pain and back pain often begin suddenly. The amount of vaginal bleeding can vary greatly, and doesn't necessarily indicate how much of the placenta has separated from the uterus. It's possible for the blood to become trapped inside the uterus, so even with a severe placental abruption, there might be no visible bleeding. In some cases, placental abruption develops slowly (chronic abruption), which can cause light, intermittent vaginal bleeding. Your baby might not grow as quickly as expected, and you might have low amniotic fluid or other complications.