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September 15 2001 • Volume 36 • Number 18

Obstetrics

Risk is at least 25%
Placenta Previa, C-Section History Up Accreta Risk

Sharon Worcester
Tallahassee Bureau

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 sonographic 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 said.

Obtain an MRI to determine the exact depth of accreta, prescribe pelvic rest after 20 weeks' gestation, administer one dose of steroids, admit the patient at 35 weeks' gestation, check for fetal lung maturity, and deliver the baby.

Because of the extensive blood loss the patient is likely to experience, consider autologous blood transfusion. Make sure the blood bank is prepared, make sure the anesthesiologist is prepared for substantial hemorrhage, and make sure the proper help is on hand.

That may include a urologist (cystoscopy is beneficial if there is suspicion that the placenta has eroded into the bladder), a vascular surgeon, an interventional radiologist, a neonatologist (most of these babies are premature), and plenty of nurses.

Also consider intraoperative ultrasound to help guide surgery, because the anatomy is “very, very, very altered and abnormal” Dr. Ferguson stressed.

If there's doubt about the ability to remove the placenta, don't try. Don't hesitate to perform a hysterectomy, particularly if the patient has multiple children.

When hysterectomy is necessary, avoid the urge to “cut and run,” he said. Performing a supracervical hysterectomy won't fix this problem, because the cervix is very vascularized and will continue to bleed, he explained.

Prepare for a 4-hour surgery with an average 4-liter blood loss. You may need to use up to 20 units of packed red blood cells, and you should be prepared for ureteral injuries, which occur in 2%-3% of patients.

Many patients require resection of at least part of the bladder, Dr. Ferguson noted.

“This is bad news. This is one of those areas where we really earn our money,” he said.