Abruption occurs when the placenta separates from the uterine wall. Most of the time, this is accompanied by vaginal bleeding as the blood travels between the membranes and the uterus. Some- times, however, there is no bleeding because edges of the placenta remain sealed.
Symptoms frequently include hypertonic uterus with severe abdominal pain and rapid contractions. If the abruption is large (more than about 50%), the fetus may not survive.
The specific cause of placental abruption is often unknown, but risk factors include abdominal trauma and maternal factors like smoking, drinking, and diabetes, among others.
Fetal distress occurs early in this condition in about half of all cases.