SAN DIEGO – An early and accurate diagnosis of placenta accreta is crucial because maternal mortality can be as high as 7% and perinatal mortality can be as high as 10%.
"Historically, the clinical presentation of placenta accreta was a prolonged third-stage or retained placenta after delivery of the baby and subsequent onset of hemorrhage or the onset of hemorrhage at the time of the termination of pregnancy," Dr. Gladys Ramos said at the University of California, San Diego, Critical Care Summer Session. "Now, with predelivery diagnosis, we have changed the management and the clinical presentation."
Placenta accreta is defined as the abnormal presence of villi attached to the myometrium due to a defect in the decidua basalis. In the 1980s, placenta accreta was believed to be rare. However, a study from 2005 showed an increase in the rate of placenta accreta (Am. J. Obstet. Gynecol. 2005;192:1458-61). The condition now occurs in 1 in every 533 pregnancies.
"Mirroring this rise is a rise in cesarean deliveries," said Dr. Ramos, a perinatologist at the UCSD Medical Center. "We think these two conditions are related. At UCSD, we take care of about 3,200 deliveries per year, and from 1990 to 2008 we have seen a linear increase in the rate of placenta accreta. We take care of about two patients per month with this condition."
Risk factors for the placenta accreta are prior uterine surgery, placenta previa, advanced maternal age, parity, and smoking. The published rate of detection by ultrasound ranges from 80% to 100%, "with a low false-positive rate," Dr. Ramos said. Telltale signs on ultrasound include loss of myometrial interface, a heterogeneous "Swiss cheese–looking" appearance to the placenta, an increase in the vascularity of the placenta, and evidence of bladder invasion.
MRI can be used as an adjunct to ultrasound diagnosis. The published detection rate with MRI ranges from 80% to 88%, "with a very low false-positive rate, which is why we use it as an adjunct to an ultrasound," she said. "We see similar findings on MRI that we do on ultrasound: thickened, dark nodular contour to the placenta; extension of the dark bands within the placenta; and mass effect causing a bulge on T1."
Nurses and sonographers at UCSD have been trained to ask patients upon presentation about risk factors for the condition." Then we look for signs of placenta accreta on ultrasound, including endovaginal ultrasound," Dr. Ramos said. "If we are concerned, we plan ahead with a multidisciplinary approach. If we’re still not sure, we proceed with MRI for diagnosis."
In 1995, clinicians at UCSD developed a multidisciplinary approach to treating patients with placenta accreta, mindful that "it took a cast of thousands to be able to make sure our outcomes were optimal for both mom and baby," said Pat Inzano, R.N., an administrative nurse in labor and delivery at UCSD. "Over the years, we’ve recognized the risk factors and the importance of early and accurate diagnosis."
The approach includes detailed maternal counseling and meticulous planning with colleagues at every conceivable step along the way in the care of the mom and baby, from neonatology and gynecologic surgery to surgical ICU staff and social workers. "When a mother gets the news [of placenta accreta], not only does she probably not understand the pathophysiology of what’s going on, but it takes a long time for her to digest this information," Ms. Inzano explained. "One of the things that’s so important at every level is getting her and her family to understand the diagnosis and reminding her that she’s [receiving] the best possible care."
The multidisciplinary team stages a conference to discuss the patient’s hospital delivery and care; availability of blood products; the need for anesthesia, surgical, and radiological expertise in house; and intensive care capability. Proper consents are also required "because the surgery will involve removing the patient’s uterus and rendering her sterile," she said. "We want to get the patient and the family as comfortable as possible with what’s going to happen. We found that providing tours of every single area that she will be ‘parking in’ is stress-relieving for her and her family, including labor and delivery and the neonatal ICU. We also provide consultations with all of the specialties involved in the case. All of this is education and counseling on a lot of different levels."
The team develops a time-line and schedules a planned delivery, including admission to the hospital, cesarean section/hysterectomy in the main operating room (OR), and unit transfers for epidural, central lines, and femoral balloons. In addition, the team coordinates a hospital tour for the patient and family. Most recommended deliveries are at week 34 because "we don’t want her to get near term and go into labor, which would aggravate a bleed of the placenta accreta," Ms. Inzano said.