Placenta Previa, C-Section History Up Accreta Risk.

ASHEVILLE, N.C. - Maintain a high index of suspicion for placenta accreta in patients with placenta previa, particularly if a patient has had a prior cesarean section, Dr. James E. Ferguson II said at the annual Southern Obstetric and Gynecologic Seminar.

In one study the rate of placenta accreta in patients with placenta previa was 5% if the patient had no prior C-sections, 25% with one prior C-section, and 50% with two or more prior C-sections, said Dr. Ferguson, who is professor and director of the division of maternal-fetal medicine at the University of Virginia in Charlottesville.

Another indication that placenta accreta may be a problem is an otherwise unexplained increase in maternal serum alpha-fetoprotein levels. The abnormal invasion of blood vessels from the placenta into the uterine wall allows excess alpha-fetoprotein into the maternal circulation.

Ultrasound findings can also reveal placenta accreta. There are four major sono-graphic findings that suggest the problem: loss of hypoechoic zone, loss of smooth muscle interface with the bladder, "Swiss cheese" placenta, and pulsatile flow to the placental sinuses, Dr. Ferguson explained.

Check for these signs in patients with risk factors, he advised.

If a patient with placenta previa and a prior C-section has a negative scan early in pregnancy, look again at around 28 weeks. Once placenta accreta is recognized by ultrasound, don't be fooled if it doesn't appear on a later ultrasound; the ability to see it may go away, but the problem doesn't.

Furthermore, if ultrasound findings reveal placenta accreta, the patient has an 80% likelihood of undergoing a hysterectomy following delivery Plan ahead, Dr. Ferguson ...