Placenta accreta is an anomaly of the ingrowth of chorial villi with invasion of the trophoblast into the basal falling off shell, myometrium, perimetrium, surrounding organs. It is manifested by the absence of signs of placenta separation, profuse uterine bleeding in the subsequent period, symptoms of involvement of adjacent organs (pelvic pain, admixture of blood in feces and urine, constipation, etc.). Pelvic ultrasound, CDM, MRI pelviometry are used for diagnosis. Treatment involves manual separation of the placenta, supravaginal amputation of the uterus, hysterectomy, metroplasty, and a bottom version of cesarean section.
Placenta accreta was first described in 1836 by the English gynecologist James Simpson, the morphological basis of the disorder was determined in 1889 by the German pathologist Frederick Hart. Over the past 50 years, there has been a more than tenfold increase in the frequency of pathology – from 1: 30,000 pregnant women in the 1950s and 60s to 1:2,500 in 2007, which is directly related to the rapid increase in the number of cesarean sections. Often, pathological deep invasion of the chorion is combined with placenta previa. According to research, after the first surgical delivery, the risk of placental tissue increment during its presentation increases by 10%, and after the 4th-5th — by 60% or more.
Causes of placenta accreta
The pathological ingrowth of chorionic villi into the uterine membranes is facilitated by both local dystrophic changes in the endometrium and blastogenesis disorders. The risk of developing the disorder increases as a woman’s age increases and the number of pregnancies she has had. According to most specialists in the field of obstetrics, the main reasons for the increment of placental tissues are:
- Cicatricial changes of the uterine wall. The prerequisites for the occurrence of local endometrial dystrophy are scars after surgical interventions, invasive manipulations — cesarean section, myomectomy, abortion, diagnostic curettage. Dystrophic changes are provoked by circulatory disorders and scarring of the epithelium.
- Diseases of the uterus. The normal architectonics of the epithelial membrane can be disrupted with nonspecific and specific endometritis caused by pathogens of chlamydia, gonorrhea, tuberculosis, and other infectious diseases of the genitals. Increment is often observed in Asherman syndrome, deformity of the uterine cavity by one large or multiple submucosal fibroid.
- High proteolytic activity of the chorion. In some cases, anomalies of blastogenesis are manifested not by violations of gametogenesis and the formation of fetal malformations, but by an increased invasive ability of the chorion. Deeper implantation is observed when the enzymatic equilibrium in the hyaluronidase – hyaluronic acid system is disturbed between the blastocyst and the decidual membrane.
Additional risk factors contributing to abnormal ingrowth of chorial villi are low placental location or presentation, multiple pregnancy, delayed pregnancy, developmental abnormalities (bicornuate uterus, the presence of an septate uterus). Pathology is more often detected in patients suffering from chronic glomerulonephritis, severe forms of gestosis, in which microcirculatory disorders are noted in various organs, including the endometrium and myometrium.
The mechanism of placenta increment is based on the discrepancy between the penetrating ability of the trophoblast and the thickness and structure of the decidual shell. Insufficient thickness of the endometrium may be due to physiological hypotrophy (the functional layer of the mucosa is usually thinner in the lower uterine segment) and pathological processes. The situation is aggravated by an increase in the proteolytic activity of enzymes that promote the introduction of blastocysts into the uterine wall. In the presence of post-traumatic, inflammatory, dystrophic changes, there is a scarring of the spongy layer of the falling placenta shell, along which its rejection occurs in the third period of labor. When the placental villi grow into the compacted tissue, their spontaneous separation from the uterine wall becomes impossible.
Significant thinning of the epithelium is accompanied by a partial or complete absence of a spongy layer. As a result, the chorial villi are separated from the myometrium by fibrinoid accumulations, and in more severe cases they are in direct contact with muscle fibers and even germinate into them to different depths. Placental septa are partially formed from myocytes, there is abundant vascularization of the myometrium, which is subject to the placental pad. After childbirth, cavernously altered muscle tissue cannot contract under the influence of oxytocin, which leads to the development of massive uterine bleeding.
The criteria for systematization of the main variants of placenta accreta are the area of abnormal attachment of placental tissue, the depth of its ingrowth into the uterus. This approach provides a more accurate prediction of complications and the choice of optimal medical tactics. The increment is complete with the involvement of the entire placenta in the process and partial with the presence of areas of normal and pathological placentation. Depending on the depth of penetration into the lining of the uterus , the following types of disorders are distinguished:
- False increment (placenta adhaerens). Has a more favorable prognosis in terms of preserving the uterus. It occurs much more often than the true one. Occurs with scarring of the spongy layer. Chorial villi grow tightly into the decidual membrane and reach the basement membrane, but do not penetrate to the myometrium. The placenta does not separate on its own, the use of special techniques for manual separation of placental tissue and uterus allows you to do without abdominal surgery.
- True increment. It develops against the background of atrophy of the spongy layer, manifested by the penetration of chorionic villi to muscle fibers (accreted placenta), into the myometrium (ingrown placenta) and beyond the uterus (sprouted placenta). Manual separation of the placenta is not possible. Often, the only method that allows you to save the life of a maternity hospital is surgical removal of the uterus. The frequency of the incremented placenta is about 78% of all cases of true increment, ingrown — 15%, sprouted — 7%.
Symptoms of placenta accretion
There are no clinical signs of the disorder during pregnancy. Pathology is manifested in childbirth by the absence of external signs of separation of the child’s place within half an hour after the expulsion of the child: the uterine floor does not rise above the navel, there is no protrusion of the placenta over the symphysis, the remaining end of the umbilical cord does not lengthen, retracts after straining the woman and shortens when pressing on the abdomen. With a complete false and true increment, postpartum bleeding does not occur, with a partial increment and an attempt to separate the ingrown afterbirth manually, profuse uterine bleeding begins. The germination of the placenta into the peritoneum and other organs is evidenced by pelvic pain of varying intensity, difficulty in defecation, an admixture of blood in the urine or feces.
In violation of blastogenesis, placenta accreta can be combined with fetal malformations, although it does not serve as their direct cause. In the prenatal period, fetoplacental insufficiency, fetal hypoxia with delayed development, premature aging of the placenta occur more often in women with placental disorders. In childbirth, the increment of placental tissue is complicated by uterine bleeding, which, without emergency assistance, can lead to significant blood loss, the occurrence of hemorrhagic shock, and the death of a woman. In rare cases, maternity patients develop air embolism, respiratory distress syndrome, DIC syndrome.
For timely detection of pathology, screening examination is carried out for all pregnant women at risk — those who have given birth multiple times, women with uterine abnormalities, low-lying or adjacent placenta, patients who have previously undergone cesarean section, myomectomy, repeated abortions. The most informative methods are ultrasound diagnostics of placenta accreta:
- Echography. Signs of possible abnormal attachment of placental tissue according to ultrasound of the uterus and fetus are considered to be a decrease in the distance between retroplacental vessels and the perimeter to 10 mm or less, the presence of cysts in the thickness of the placenta, hyperechoic inclusions. The probability of increment increases with the detection of hypo- and anechoic areas with lacunar blood flow in the muscular wall of the uterus.
- Color Doppler mapping (CDM). The method is considered the gold standard in prenatal increment diagnosis. During the study, the localization of abnormal vascular zones is accurately determined. The pathognomonic sign of the disorder is the expansion of the subplacental venous complex. The CDM also provides an accurate assessment of the depth of penetration of chorial villi into the myometrium.
In recent years, for diagnostic purposes, obstetricians and gynecologists have increasingly prescribed MRI pelviometry, which allows in doubtful cases to reliably visualize the irregularities of the uterine wall, pathological heterogeneity of the structure of the myometrium and placental tissue. An indirect laboratory sign of the disorder is an increase in the level of alpha-fetoprotein.
When detecting pathology in childbirth, it is important to quickly perform a differential diagnosis between false and true increment using manual separation of the afterbirth. With tight attachment, the placental tissue can be completely separated and, thus, profuse bleeding can be stopped. The true increment is evidenced by the impossibility of separating the placenta in a single array, tissue ruptures, and the absence of individual lobules remaining in the uterus. The disease is differentiated from other disorders accompanied by massive uterine bleeding: uterine hypotension, DIC syndrome, coagulopathies, pregnancy with a normally attached placenta in the tubal corner of a doubled or two-horned uterus, etc. According to the indications, the patient is consulted by a urologist, proctologist, surgeon, anesthesiologist-resuscitator.
Treatment of placenta accretion
The detection of pathology serves as an indication for surgical intervention. With antenatal diagnosis of increment, natural childbirth is contraindicated, the operation is performed as planned at 37-39 weeks of gestational age simultaneously with cesarean section, if detected in childbirth — urgently for vital indications. The recommended amount of intervention is determined by the type of placenta increment:
- Manual separation with the release of the afterbirth. An obstetric manual for the extraction of an undelivered placenta with fetal membranes is carried out under intravenous anesthesia with a false increment. During the intervention, the obstetrician separates and removes the tightly attached placental tissue manually.
- Removal of the uterus. When chorionic villi penetrate to the myometrium or grow into smooth muscle fibers, supravaginal amputation or hysterectomy is traditionally performed. Despite the trauma, until recently, such operations were the only way to stop bleeding.
- Organ-preserving interventions. Antenatal diagnostics followed by a bottom caesarean section or metroplasty allows you to save the uterus even with a true increment.
When the uterine wall germinates, combined urogynecological and proctogynecological interventions aimed at complete removal of placental tissue are recommended. Often, sparing surgical methods are supplemented with endovascular ones to prevent or stop uterine bleeding (uterine artery embolization, temporary balloon occlusion). During an emergency operation, the maternity hospital is shown to restore the volume of circulating blood with infusion therapy (transfusion of whole blood, its components, colloidal and crystalloid solutions). Symptomatic treatment includes the appointment of uterotonics (while preserving the uterus), hemostatics, medications to maintain pressure and cardiac activity.
Prognosis and prevention
A favorable outcome of placenta accreta is possible only with timely diagnosis and selection of the optimal treatment method. To improve the prognosis, antenatal screening and planned surgical delivery with the recommended volume of surgery are used. Primary prevention involves the rejection of unreasonable diagnostic and therapeutic intrauterine interventions, pregnancy planning, treatment of inflammatory diseases of the uterus, caesarean section strictly in the presence of obstetric or extragenital indications.