October 2000 I attended a 5 day Maternal-Fetal Medicine Conference
One of the presentations was on abnormal placentation, especially the increased incidence and surgical treatment of placenta accreta /percreta.
The following article is a distillation of that information and recommendations based on this material, especially as it applies to Cesarean prevention and VBAC management for community midwives.
VBAC Alert -
Placenta Previa / Accreta / Percreta
as a sequelea of Cesarean and other Uterine Surgery
Accreda /percreda is life-threatening complication of pregnancy that is significantly increased in the United States over the last 20 years due to an order of magnitude increase in gyn instrumentation of the uterus and Cesarean deliveries.
CME review article #24 for 1998 Diagnosis and Management of Placenta Pecreda: A Review
"The higher incidence of cesarean delivery today is strongly associated with the greater frequency of placenta previa, which has increased from 1 in 1000 pregnancies in 1950 to 101 in 1000 in 1985 (Clark S, Koonings P, Phelan J. Placenta previa/accreta & prior cesarean section. Obste Gynecol 1985;66, pages 89-92) Given the known association between placenta previa and placenta accreta /percreta, it is logical to assume that the increased cesarean delivery rate has directly contributed to the rising incidence of placenta accreta/percreta."
"Distinction between accreta and percreta can be difficult before delivery. .... In this review we use both terms interchangeably."
A well known but generally unacknowledged complication of prior CS is a dramatic increase in abnormal placental implantation in a future pregnancy, including previa and accreda. This is another compelling reason, in an already lengthy list of reasons, to prevent primary CSs whenever possible.
Accreda/percreda is a potentially fatal complication for the mother due to hemorrhage as blood loss typically ranges from 3000 mls to 5000 mls. Other potentially fatal complications includes Disseminating Intravascular Coagulation (DIC), which can result in death or amputation of lower limbs, transfusion reactions, other complications accompanying blood transfusions such as HIV or hepatitis, allo-immunization, fluid overload, and less commonly, infection and multiple organ failure. Surgical morbidity includes: emergency hysterectomy, bowel injury, urological injuries including ureteral trauma and bladder lacerations requiring surgical resection. Patients with accreda/percreda are at increased risk for blood clots (for example pulmonary embolism) and Adult Respiratory Distress Syndrome (ARDS).
Accreta/percreta is complication of pregnancy that is massive and life threatening, irrespective of its antecedents. It is additionally tragic when its underlying cause is iatragenic, such as a predictable sequelea of CS done for trivial reasons such as automatic CS for breech baby resorted to because no physician had vaginal breech skills or institutional policies or D&Cs done routinely for miscarriages, absent excessive or prolonged bleeding.
The association between invasive uterine procedures and surgery should be widely known by the public, just as the complications of blood transfusions (Hepatitis, HIV), the tetragenic effects of thalidomide and the association of smoking to lung disease and fetal growth restriction. Women with infertility problems need to know that some uterine diagnostic procedures can put their life at risk if they do conceive. Women having a miscarriage should consider carefully the option of D&C as a method to bring about a quick end to the anxiety of a failed pregnancy and vaginal bleeding (aside from serious hemorrhage requiring immediate surgical intervention to preserve her life). Patients for whom myomectomy is recommended (removal of fibroid tumors of the uterus) should also to made aware of these risks as a part of the informed consent and decision making process.
Medical management of Abnormal Placententation
Optimal management of women with placenta accreta is complex, expensive and intensive at a level reminiscent of brain surgery or organ transplant. Operating room times are typically 3 hrs if emergency hysterectomy is not required, 4 1/2 hours if it is. It is appropriate that women receive "informed consent" relative to the well-known risks of invasive fertility procedures, post-miscarriage D&C and elective termination of pregnancy and of course, Cesarean surgery.
Surgical realities facing the mother and surgeon:
Placental Percreta is a pernicious condition in which the placenta acts like an invading tumor. The theory for why an abnormal placental implementation is associated with prior instrumentation or surgical incision of the uterus has to do with uterine scar tissue. The formative placental tissue (thromboblastic cells) normally seek out a generous blood supply. Since scar tissue is connective (i.e. no blood vessels within) the placental tissue grows through it and on towards other vascular structures. It would seem that something about this abnormal process fails to trigger the end cells. In severe case this abnormal placentation grows completely through the uterus and actually physically replaces the uterine wall and sometimes grows into the bladder. Unlike the strong muscular tissue of the uterus, placental tissue lacks the muscular structure and is in fact very fragile. If a placenta percreta completely replaces uterine wall, the mother may have a spontaneous uterine rupture (even if she is a primagravida without any prior uterine surgery). This could cause the death of both mother and baby.
This type of abnormal placentation often produces a distortion of the uterus that can be seen as soon as the uterus is exposed by the surgery. Assuming it is an anterior location, a large "bulge" appears on the lower half, similar to textbook photos of a pregnant woman's abdomen with a full bladder. Lower anterior wall implantation is the typical post CS scenario location for abnormal placentation.
In addition to crowding out normal tissue of the uterus and bladder, it also give rise to "rosette" of free-ranging blood vessels. Healthcare providers will be familiar with a velamentous placenta in which blood vessels grow out across the amniotic membranes. Unfortunately, this same mechanism occurs in abnormal placentation. These large vessels can rupture anytime during pregnancy or the intrapartum causing internal fetal hemorrhage. Often these rosettes of vessel can be seen on ultrasound if done by a skilled sonographer who has been asked to specifically evaluate the women for placental position and any indication of AIP. This may be the first tip-off for accreta/ increta/ percreta. Obviously you do not want to see a low-implanted anterior placenta in a VBAC mom!
Preparation for Surgical Treatment of A/I/P
In the weeks before scheduled surgery the mother may be treated to prevent anemia by using a glycoprotein hormone that is produced by using recombinant DNA technology. The drug is called erythropoitin and it increases red blood cell mass by stimulating bone marrow. It is given either subcutaneously or intravenously in a does of 50 to 100 unites per kilogram of the women's body weight over the two weeks before scheduled surgery.
In the days preceding the scheduled surgery the obstetrician will need to arrange for massive blood transfusions as average blood loss for cesarean hysterectomy is between 3000 and 5000 ml (equal to or greater than total blood volume for the mother). If the required amount of blood (8 to 10 units/pints at start of surgery, with at least that amount blood units available in reserve) is not easily available in the chosen hospital, then surgery should be moved to a bigger institution
Surgical Treatment of Placenta Accreta/Percreta
The course of medical/surgical treatment required to deal with placenta accreta/increta/percreta (A/I/P) is a regime reminiscent of major brain surgery or an organ transplant. However, the ability to diagnosis A/I/P before the spontaneous labor (and eventual massive spontaneous hemorrhage!) greatly improves the likelihood of the mother living through the ordeal, perhaps with her uterus intact (rarely but occasionally possible if the placenta is determined to be only an accreta, as percreta grows into the uterine wall and always necessitates a cesarean to prevent fatal hemorrhage).
For scheduled surgery, the following list of surgical specialists and assistants will be necessary -
senior OR technician familiar with massive hemorrhage
two circulating nurses
vascular or gyn onocology surgeon
ICU during immediate recovery
additional equipment required:
2 suction machines, spare suction bottles
cell save machine
10 units of cross-matched blood up front,
10 more immediately available
Appropriate balloon catheters for internal iliac, hypogastric and uterine arteries, to occlude large arteries used to stop massive hemorrhage when other
Procedures done to the woman after being moved to the operating room are:
Acute normovolemic hemodilution -- withdrawal of 1-3 pints of her own blood and replacement with saline IV This blood will be returned to her during the surgery as needed.
The mother will also need 2 or more IV lines with large bore needles (14 or 16 gauge) as well as central arterial lines with Swan-Ganz catheter, naso-gastric tube, and a body warmer under her body (reduces the physiological stress of surgery).
Intra-operative procedures in addition to cesarean delivery & removal of adherent placenta (or hysterectomy with placenta left in place) include the following:
Cystoscopy and placement of renal stents (insertion of a small device, marking the place where each ureter comes into the bladder, done to help to the surgeon identify the ureters during surgery)
Surgical Dilemma / surgical technique: After the previously mentioned pre-operative procedures, the abdomen is opened with a very large vertical incision from pubic bone to above umbilicus so the pregnant uterus can be externalized. This is necessary so appropriate visualization/ inspection can be accomplished, looking for placement of the placenta, evidence of encroachment of other organs and bleeding into other structures. Then the obstetrician must make an incision into the pregnant uterus for the cesarean extraction of the infant without cutting into the placenta. Most usually this is either a classically incision in the fundus. If the placenta is adherent to the anterior wall the uterus must be torqued to the side and incised on the posterior surface.
If lucky, it may be possible to manually remove a placenta accreta and successfully control bleeding without performing a hysterectomy. Placenta percreta however universally requires that a hysterectomy be performed and so no attempt is made to remove the placenta. In that case the uterus is clamped or stitched back up with the placenta still in place and a hysterectomy is performed. This often requires an incision into the bladder to cut away that part of the bladder wall where the placenta has grown into the dome of the bladder.
Intraoperative bleeding is brisk due to the vascularity of these structures. It should be remembered that 500 to 750 cc of blood (1 to 1 1/2 pints) perfuse the uterus per minute. Techniques to control hemorrhage include tying, clamping or use of balloon catheters to occlude the hypogastric, internal iliac, uterine artery or even the descending aorta. For this reason the expertise of a vascular or oncology gynecologist are helpful for this part of the surgery. A cell saver machine helps to "harvest" lost maternal blood so that the mother can be transfused with her own blood as much as possible.
In spite of this impressive list of medical expertise, 10% of women with placenta percreta die of its complications, most usually from hemorrhage or the complications of blood transfusions, infection or multiple organ failure.
The purpose of this detailed description of abnormal placentation and percreta surgery is to bring home the reality of this massive complication, in an attempt to reduce the preventable instances of it by helping to reduce the number of unnecessary Cesareans.
Many have observed that knowledge is power. Individual power for childbearing women is the ability to make the best choices and for practitioners, it is the ability to offer the best information for informed consent. Prevention is clearly the best of all "treatments" for these major life-threatening problems, which are increasing in number due to an increase in electively performed Cesarean surgery. Reduction in CS and non-essential instrumentation of the uterus reduces the incidence of placenta previa (which necessitates CS delivery) and its more malignant form, accreta and percreta which necessitates cesarean hysterectomy. Reducing cesareans saves maternal lives and preserves normal childbearing abilities. Prevention of unnecessary CSs also reduces the number of subsequent VBAC labors and the dilemma that presents for mothers who want to labor at home and the midwives who attend them.
Recommendation for midwives to reduce the risks associated with spontaneous labor and birth in women with previous instrumentation of the uterus, including previous cesarean:
Pay particular attentions to mother's history of medical procedures and circumstances of her health and fertility history.
1) Non-obstetrical History - concentrate questions on uterine invasive past gyn surgery -- D&C, hysteroscopy, myomectomy
2) Previous Pregnancy Outcomes - any miscarriages, especially with following D&C, tubal pregnancy, close spacing of term pregnancies (increases risk of previa)
3) OB hx -- previous PPH, retained placenta, D&C following PPH/retained placenta, previous CS
Current Circumstances: Anemia, especially with a short interval between last and present pregnancy -- research suggests that there is an increased vascularization in women who begin pregnancy with significant anemia, increasing the likelihood of abnormal placental implementation. This is another good for telling women to take folic acid supplements pre-conceptionally (also reduces neural tube defects in the baby).
Second trimester pregnancies with elevated MSAFP/triple screen with unexplained elevated HCG -- have a higher level of suspicion as there is a statistical association between abnormal placentation and elevated HCG level.
Benefits of Targeted Ultrasound
For women with identified precursors to abnormal placental implementation, a high quality ultrasound can be life and uterus-saving for the mother. A single ultrasound in the first trimester of pregnancy may NOT reveal the needed information unless it identifies a fundal or posterior placenta in the upper pole of the uterus. Any low-lying or previa identified in the early weeks of pregnancy should be re-evaluated in 3rd trimester.
A level II ultrasound at 28-32 wks for all mothers with a history of uterine instrumentation who are planning an OOH labor is prudent. This includes a color Doppler and should be done by an experienced technician who specializes in high- risk obstetrics or urology.
Four ultrasound findings specific for a morbidly adherent placenta:
loss of the hypo-echoic zone (reduced echo)
loss of smooth interface with bladder
"Swiss-cheese" (vascular lacunae)
focal nodular projections beyond the uterus
Pertinent Color flow and Power Doppler findings:
chaotic type flow between placenta and bladder
pulsatile (pulsing) flow in bladder wall
pulsatile flow though the thickness of the placenta in places
If there is any reasons to suspect accreda from the above ultrasound finding a 3-D ultrasound or MRI is the next diagnostic tool:
3-D ultrasound finds:
"rosette" of vessels protruding from placenta into the bladder (may sometimes be seen on routine ultrasound by a very astute sonographer)
Other ultrasound-relative accreda info:
a single early ultrasound may not be enough
an accreta/percreta is almost always diagnosed in association with placenta previa
placenta accreda may develop/worsen as pregnancy progresses
placenta accreda NEVER resolves with advancing pregnancy
ultrasound finding of accreda are associated with an 80% likelihood of needing an emergency hysterectomy.
Delivery for these women needs to be in a major medical center.
OOH labor for VBAC mothers
OOH labor for VBAC mothers is (and no doubt will remain) controversial. It must be acknowledged how difficult it would be to justify planning to labor at home were a uterine rupture to occur so far removed from surgical facilities. The ideal resolution to the controversy of VBAC management is to prevent the primary CS but that is of little help to women who have already had uterine instrumentation or surgery. For the foreseeable future the VBAC situation will remain a dilemma for everyone. Obstetricians continue to feel obligated to impress higher and higher levels of routine surveillance/ pitocin induction/ augmentation for hospital patients while Midwives will continue to agonize over whether or not offer domiciliary care. And mothers, whose only choices at present is between the hypermedicalizm of the current "standard" hospital care which, for many, will result in another CS, will continue to have to choose between the devil and the deep blue sea.