Placental Abruption Risk After Subchorionic Hematoma (SCH)

Question
I am 27 with a two-year-old son.  I was 35 weeks today, April 9th, lmp 8/6/05.  In my first tri-mester, I was diagnosed with a large Subchorionic Hematoma.  It went away towards the end of my first tri-mester and, luckily, I haven't had any further complications.  I have heard that women that have had SCH's are more likely to experience placental abruption or placenta previa.  Could you please tell me what you know about this.  Also, if I am at risk, what symptoms should I be looking for and what diagnostic tests should I be asking for?  Thank you.

Answer
A subchorionic hematoma is merely a sequestration of blood in the folds of the developing placenta. Once the blood dissipates, there usually is no further problem. It is not a risk for placenta previa. Placenta previa is caused by a placenta that situates itself on top of the cervical os (the opening of the uterus). Usually a placenta previa will  disappear by 24 weeks gestation. If it remains covering the opening of your uterus, you would be delivered by cesarean section to avoid hemorrhage in labor. A  placental abruption (premature separation of the placenta) can be can occur  around term or earlier.It is usually accompanied with severe cramps. Depending on where the hematoma was in early pregnancy there may be a slightly higher risk of Abruption. However, there is nothing you can do to predict it and it is very, very rare. If you have any heavy vaginal bleeding before you co into labor, tell your doctor.