Placenta accreta spectrum

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Placenta accreta
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Types of placenta accreta
Specialty Obstetrics

Placenta accreta occurs when all or part of the placenta attaches abnormally to the myometrium (the muscular layer of the uterine wall). Three grades of abnormal placental attachment are defined according to the depth of attachment and invasion into the muscular layers of the uterus:

Contents

  1. Accreta – chorionic villi attached to the myometrium, rather than being restricted within the decidua basalis .
  2. Increta – chorionic villi invaded into the myometrium.
  3. Percreta – chorionic villi invaded through the perimetrium (uterine serosa).

Because of abnormal attachment to the myometrium, placenta accreta is associated with an increased risk of heavy bleeding at the time of attempted vaginal delivery. The need for transfusion of blood products is frequent, and surgical removal of the uterus (hysterectomy) is sometimes required to control life-threatening bleeding. [1]

Rates of placenta accreta are increasing. As of 2016, placenta accreta affects an estimated 1 in 272 pregnancies. [2]

Risk factors

An important risk factor for placenta accreta is placenta previa in the presence of a uterine scar. Placenta previa is an independent risk factor for placenta accreta. Additional reported risk factors for placenta accreta include maternal age and multiparity, other prior uterine surgery, prior uterine curettage, uterine irradiation, endometrial ablation, Asherman syndrome, uterine leiomyomata, uterine anomalies, and smoking.

The condition is increased in incidence by the presence of scar tissue i.e. Asherman's syndrome usually from past uterine surgery, especially from a past dilation and curettage, [3] (which is used for many indications including miscarriage, termination, and postpartum hemorrhage), myomectomy, [4] or caesarean section. A thin decidua can also be a contributing factor to such trophoblastic invasion. Some studies suggest that the rate of incidence is higher when the fetus is female. [5] Other risk factors include low-lying placenta, anterior placenta, congenital or acquired uterine defects (such as uterine septa), leiomyoma, ectopic implantation of placenta (including cornual pregnancy). [6] [7] [8]

Pregnant women above 35 years of age who have had a caesarian section and now have a placenta previa overlying the uterine scar have a 40% chance of placenta accreta. [9]

Pathogenesis

The placenta forms an abnormally firm and deep attachment to the uterine wall. There is absence of the decidua basalis and incomplete development of the Nitabuch's layer. [10] There are three forms of placenta accreta, distinguishable by the depth of penetration.

TypeFractionDescription
Placenta accreta75–78%The placenta attaches strongly to the myometrium, but does not penetrate it. This form of the condition accounts for around 75% of all cases.
Placenta increta17%Occurs when the placenta penetrates the myometrium.
Placenta percreta5–7%The highest-risk form of the condition occurs when the placenta penetrates the entire myometrium to the uterine serosa (invades through entire uterine wall). This variant can lead to the placenta attaching to other organs such as the rectum or urinary bladder.

Diagnosis

When the antepartum diagnosis of placenta accreta is made, it is usually based on ultrasound findings in the second or third trimester. Sonographic findings that may be suggestive of placenta accreta include:

Unfortunately, the diagnosis is not easy and is affected by a significant interobserver variability. [11] In doubtful cases it is possible to perform a nuclear magnetic resonance (MRI) of the pelvis, which has a very good sensitivity and specificity for this disorder. [12] MRI findings associated with placenta accreta include dark T2 bands, bulging of the uterus, and loss of the dark T2 interface. [13]

Although there are isolated case reports of placenta accreta being diagnosed in the first trimester or at the time of abortion <20 weeks' gestational age, the predictive value of first-trimester ultrasound for this diagnosis remains unknown. Women with a placenta previa or "low-lying placenta" overlying a uterine scar early in pregnancy should undergo follow-up imaging in the third trimester with attention to the potential presence of placenta accreta.

Complications

The exact incidence of maternal mortality related to placenta accreta and its complications is unknown, but it is significant, [14] especially if the urinary bladder is involved [15]

Treatment

Treatment may be delivery by caesarean section and abdominal hysterectomy if placenta accreta is diagnosed before birth. [16] [17] Oxytocin and antibiotics are used for post-surgical management. [18] When there is partially separated placenta with focal accreta, best option is removal of placenta. If it is important to save the woman's uterus (for future pregnancies) then resection around the placenta may be successful. Conservative treatment can also be uterus sparing but may not be as successful and has a higher risk of complications. [17] Techniques include:

In cases where there is invasion of placental tissue and blood vessels into the bladder, it is treated in similar manner to abdominal pregnancy and manual placental removal is avoided. However, this may eventually need hysterectomy and/or partial cystectomy. [10]

If the patient decides to proceed with a vaginal delivery, blood products for transfusion and an anesthesiologist are kept ready at delivery. [19]

Epidemiology

The reported incidence of placenta accreta has increased from approximately 0.8 per 1000 deliveries in the 1980s to 3 per 1000 deliveries in the past decade.

Incidence has been increasing with increased rates of caesarean deliveries, with rates of 1 in 4,027 pregnancies in the 1970s, 1 in 2,510 in the 1980s, and 1 in 533 for 1982–2002. [20] In 2002, ACOG estimated that incidence has increased 10-fold over the past 50 years. [8] The risk of placenta accreta in future deliveries after caesarian section is 0.4-0.8%. For patients with placenta previa, risk increases with number of previous caesarean sections, with rates of 3%, 11%, 40%, 61%, and 67% for the first, second, third, fourth, and fifth or greater number of caesarean sections. [21]

Related Research Articles

Dilationand curettage (D&C) refers to the dilation (widening/opening) of the cervix and surgical removal of part of the lining of the uterus and/or contents of the uterus by scraping and scooping (curettage). It is a gynecologic procedure used for diagnostic and therapeutic purposes, and is the most commonly used method for first-trimester miscarriage or abortion.

Caesarean section Surgical procedure in which a baby is delivered through an incision in the mothers abdomen

Caesarean section, also known as C-section or caesarean delivery, is the surgical procedure by which one or more babies are delivered through an incision in the mother's abdomen, often performed because vaginal delivery would put the baby or mother at risk. Reasons for the operation include obstructed labor, twin pregnancy, high blood pressure in the mother, breech birth, and problems with the placenta or umbilical cord. A caesarean delivery may be performed based upon the shape of the mother's pelvis or history of a previous C-section. A trial of vaginal birth after C-section may be possible. The World Health Organization recommends that caesarean section be performed only when medically necessary. Some C-sections are performed without a medical reason, upon request by someone, usually the mother.

Obstetrics is the field of study concentrated on pregnancy, childbirth and the postpartum period. As a medical specialty, obstetrics is combined with gynecology under the discipline known as obstetrics and gynecology (OB/GYN), which is a surgical field.

Placenta praevia Medical condition

Placenta praevia is when the placenta attaches inside the uterus but in an abnormal position near or over the cervical opening. Symptoms include vaginal bleeding in the second half of pregnancy. The bleeding is bright red and tends not to be associated with pain. Complications may include placenta accreta, dangerously low blood pressure, or bleeding after delivery. Complications for the baby may include fetal growth restriction.

Ashermans syndrome Medical condition

Asherman's syndrome (AS) is an acquired uterine condition that occurs when scar tissue (adhesions) form inside the uterus and/or the cervix. It is characterized by variable scarring inside the uterine cavity, where in many cases the front and back walls of the uterus stick to one another. AS can be the cause of menstrual disturbances, infertility, and placental abnormalities. Although the first case of intrauterine adhesion was published in 1894 by Heinrich Fritsch, it was only after 54 years that a full description of Asherman syndrome was carried out by Joseph Asherman. A number of other terms have been used to describe the condition and related conditions including: uterine/cervical atresia, traumatic uterine atrophy, sclerotic endometrium, and endometrial sclerosis.

Placental abruption Medical condition

Placental abruption is when the placenta separates early from the uterus, in other words separates before childbirth. It occurs most commonly around 25 weeks of pregnancy. Symptoms may include vaginal bleeding, lower abdominal pain, and dangerously low blood pressure. Complications for the mother can include disseminated intravascular coagulopathy and kidney failure. Complications for the baby can include fetal distress, low birthweight, preterm delivery, and stillbirth.

Adenomyosis Extension of endometrial tissue into the myometrium

Adenomyosis is a medical condition characterized by the growth of cells that proliferate on the inside of the uterus (endometrium) atypically located among the cells of the uterine wall (myometrium), as a result, thickening of the uterus occurs. As well as being misplaced in patients with this condition, endometrial tissue is completely functional. The tissue thickens, sheds and bleeds during every menstrual cycle.

Antepartum bleeding, also known as antepartum haemorrhage (APH) or prepartum hemorrhage, is genital bleeding during pregnancy after the 28th week of pregnancy up to delivery.

Obstetrical bleeding is bleeding in pregnancy that occurs before, during, or after childbirth. Bleeding before childbirth is that which occurs after 24 weeks of pregnancy. Bleeding may be vaginal or less commonly into the abdominal cavity. Bleeding which occurs before 24 weeks is known as early pregnancy bleeding.

Uterine rupture Medical condition

Uterine rupture is when the muscular wall of the uterus tears during pregnancy or childbirth. Symptoms, while classically including increased pain, vaginal bleeding, or a change in contractions, are not always present. Disability or death of the mother or baby may result.

Uterine atony Loss of tone in the uterine musculature

Uterine atony is the failure of the uterus to contract adequately following delivery. Contraction of the uterine muscles during labor compresses the blood vessels and slows flow, which helps prevent hemorrhage and facilitates coagulation. Therefore, a lack of uterine muscle contraction can lead to an acute hemorrhage, as the vasculature is not being sufficiently compressed. Uterine atony is the most common cause of postpartum hemorrhage, which is an emergency and potential cause of fatality. Across the globe, postpartum hemorrhage is among the top five causes of maternal death. Recognition of the warning signs of uterine atony in the setting of extensive postpartum bleeding should initiate interventions aimed at regaining stable uterine contraction.

In case of a previous caesarean section a subsequent pregnancy can be planned beforehand to be delivered by either of the following two main methods:

Postpartum bleeding Loss of blood following childbirth

Postpartum bleeding or postpartum hemorrhage (PPH) is often defined as the loss of more than 500 ml or 1,000 ml of blood within the first 24 hours following childbirth. Some have added the requirement that there also be signs or symptoms of low blood volume for the condition to exist. Signs and symptoms may initially include: an increased heart rate, feeling faint upon standing, and an increased breathing rate. As more blood is lost, the patient may feel cold, blood pressure may drop, and they may become restless or unconscious. The condition can occur up to six weeks following delivery.

Vasa praevia Condition in which fetal blood vessels cross or run near the internal opening of the uterus.

Vasa praevia is a condition in which fetal blood vessels cross or run near the internal opening of the uterus. These vessels are at risk of rupture when the supporting membranes rupture, as they are unsupported by the umbilical cord or placental tissue.

Velamentous cord insertion Velamentous placenta

Velamentous cord insertion is a complication of pregnancy where the umbilical cord is inserted in the fetal membranes. It is a major cause of antepartum hemorrhage that leads to loss of fetal blood and associated with high perinatal mortality. In normal pregnancies, the umbilical cord inserts into the middle of the placental mass and is completely encased by the amniotic sac. The vessels are hence normally protected by Wharton's jelly, which prevents rupture during pregnancy and labor. In velamentous cord insertion, the vessels of the umbilical cord are improperly inserted in the chorioamniotic membrane, and hence the vessels traverse between the amnion and the chorion towards the placenta. Without Wharton's jelly protecting the vessels, the exposed vessels are susceptible to compression and rupture.

Placental disease Medical condition

A placental disease is any disease, disorder, or pathology of the placenta.

Cervical pregnancy Medical condition

A cervical pregnancy is an ectopic pregnancy that has implanted in the uterine endocervix. Such a pregnancy typically aborts within the first trimester, however, if it is implanted closer to the uterine cavity – a so-called cervico-isthmic pregnancy – it may continue longer. Placental removal in a cervical pregnancy may result in major hemorrhage.

Early pregnancy bleeding refers to vaginal bleeding before 24 weeks of gestational age. If the bleeding is significant, hemorrhagic shock may occur. Concern for shock is increased in those who have loss of consciousness, chest pain, shortness of breath, or shoulder pain.

The anomaly scan, also sometimes called the anatomy scan, 20-week ultrasound, or level 2 ultrasound, evaluates anatomic structures of the fetus, placenta, and maternal pelvic organs. This scan is an important and common component of routine prenatal care. The function of the ultrasound is to measure the fetus so that growth abnormalities can be recognized quickly later in pregnancy, and to assess for congenital malformations and multiple pregnancies.

Sally Collins

Sally L. Collins BSc BMBCh DPhil FRCOG is an Associate Professor of Obstetrics in the Nuffield Department of Women’s and Reproductive Health, University of Oxford and a Consultant Obstetrician subspecializing in Feto-Maternal Medicine at the John Radcliffe Hospital, Oxford. She is also a lecturer in Medical Sciences at St. Anne’s College, University of Oxford.

References

  1. ↑ Smith, Zachary L.; Sehgal, Shailen S.; Arsdalen, Keith N. Van; Goldstein, Irwin S. (2014). "Placenta Percreta With Invasion into the Urinary Bladder". Urology Case Reports. 2 (1): 31–32. doi:10.1016/j.eucr.2013.11.010. PMC   4733000 . PMID   26955539.
  2. ↑ Society of Gynecologic Oncology; American College of Obstetricians and Gynecologists and the Society for Maternal–Fetal Medicine; Cahill, Alison G.; Beigi, Richard; Heine, R. Phillips; Silver, Robert M.; Wax, Joseph R. (2018-12-01). "Placenta Accreta Spectrum". American Journal of Obstetrics and Gynecology. 219 (6): B2–B16. doi: 10.1016/j.ajog.2018.09.042 . ISSN   1097-6868. PMID   30471891.
  3. ↑ Capella-Allouc, S.; Morsad, F; Rongières-Bertrand, C; Taylor, S; Fernandez, H (1999). "Hysteroscopic treatment of severe Asherman's syndrome and subsequent fertility". Human Reproduction. 14 (5): 1230–3. doi: 10.1093/humrep/14.5.1230 . PMID   10325268.
  4. ↑ Al-Serehi, A; Mhoyan, A; Brown, M; Benirschke, K; Hull, A; Pretorius, DH (2008). "Placenta accreta: An association with fibroids and Asherman syndrome". Journal of Ultrasound in Medicine. 27 (11): 1623–8. doi:10.7863/jum.2008.27.11.1623. PMID   18946102. S2CID   833810.
  5. ↑ American Pregnancy Association (January 2004) 'Placenta Accreta Archived 2006-01-16 at the Wayback Machine '. Accessed 16 October 2006
  6. ↑ Arulkumaran, Sabaratnam (2009). Warren, Richard (ed.). Best practice in labour and delivery (1st ed., 3rd printing. ed.). Cambridge: Cambridge University Press. pp. 108, 146. ISBN   978-0-521-72068-7.
  7. ↑ Shimonovitz, S; Hurwitz, A; Dushnik, M; Anteby, E; Geva-Eldar, T; Yagel, S (September 1994). "Developmental regulation of the expression of 72 and 92 kd type IV collagenases in human trophoblasts: a possible mechanism for control of trophoblast invasion". American Journal of Obstetrics and Gynecology. 171 (3): 832–8. doi:10.1016/0002-9378(94)90107-4. PMID   7522400.
  8. 1 2 ACOG Committee on Obstetric, Practice (January 2002). "ACOG Committee opinion. Number 266, January 2002 : placenta accreta". Obstetrics and Gynecology. 99 (1): 169–70. doi:10.1016/s0029-7844(01)01748-3. PMID   11777527.
  9. ↑ Hobbins, John C. (2007). Obstetric ultrasound: artistry in practice. Oxford: Blackwell. p. 10. ISBN   978-1-4051-5815-2.
  10. 1 2 Steven G. Gabbe; Jennifer R. Niebyl; Joe Leigh Simpson, eds. (2002). Obstetrics: normal and problem pregnancies (4. ed.). New York, NY [u.a.]: Churchill Livingstone. p. 519. ISBN   9780443065729.
  11. ↑ Bowman ZS, Eller AG, Kennedy AM, Richards DS, Winter TC, Woodward PJ, Silver RM (December 2014). "Interobserver variability of sonography for prediction of placenta accreta". Journal of Ultrasound in Medicine. 33 (12): 2153–8. doi: 10.7863/ultra.33.12.2153 . PMID   25425372. S2CID   22246937.
  12. ↑ D'Antonio F, Iacovella C, Palacios-Jaraquemada J, Bruno CH, Manzoli L, Bhide A (July 2014). "Prenatal identification of invasive placentation using magnetic resonance imaging: systematic review and meta-analysis". Ultrasound in Obstetrics & Gynecology. 44 (1): 8–16. doi:10.1002/uog.13327. PMID   24515654. S2CID   9237117.
  13. ↑ Balcacer, Patricia; Pahade, Jay; Spektor, Michael; Staib, Lawrence; Copel, Joshua A.; McCarthy, Shirley (2016). "Magnetic Resonance Imaging and Sonography in the Diagnosis of Placental Invasion". Journal of Ultrasound in Medicine. 35 (7): 1445–1456. doi: 10.7863/ultra.15.07040 . ISSN   0278-4297. PMID   27229131.
  14. ↑ Selman AE (April 2016). "Caesarean hysterectomy for placenta praevia/accreta using an approach via the pouch of Douglas". BJOG: An International Journal of Obstetrics and Gynaecology. 123 (5): 815–9. doi:10.1111/1471-0528.13762. PMC   5064651 . PMID   26642997.
  15. ↑ Washecka R, Behling A (April 2002). "Urologic complications of placenta percreta invading the urinary bladder: a case report and review of the literature". Hawaii Medical Journal. 61 (4): 66–9. PMID   12050959.
  16. ↑ Johnston, T A; Paterson-Brown, S (January 2011). Placenta Praevia, Placenta Praevia Accreta and Vasa Praevia: Diagnosis and Management. Green-top Guideline No. 27. Royal College of Obstetricians and Gynecologists.
  17. 1 2 Oyelese, Yinka; Smulian, John C. (2006). "Placenta Previa, Placenta Accreta, and Vasa Previa". Obstetrics & Gynecology. 107 (4): 927–41. doi:10.1097/01.AOG.0000207559.15715.98. PMID   16582134. S2CID   22774083.
  18. 1 2 Turrentine, John E. (2008). Clinical protocols in obstetrics and gynecology (3rd ed.). London: Informa Healthcare. p. 286. ISBN   9780415439961.
  19. ↑ Committee On Obstetric, Practice (2002). "Placenta accreta Number 266, January 2002 Committee on Obstetric Practice". International Journal of Gynecology & Obstetrics. 77 (1): 77–8. doi:10.1016/S0020-7292(02)80003-0. PMID   12053897. S2CID   42076480.
  20. ↑ Committee on Obstetric Practice. "Placenta Accreta". American College of Obstetricians and Gynecologists. Archived from the original on 2016-11-23. Retrieved 2014-08-22.
  21. ↑ Silver, R.M.; Landon, M.B.; Rouse, D.J.; Leveno, K.J.; Spong, C.Y.; Thom, E.A.; Moawad, A.H.; Caritis, S. N.; Harper, M.; Wapner, R. J.; Sorokin, Y; Miodovnik, M; Carpenter, M; Peaceman, A. M.; O'Sullivan, M. J.; Sibai, B.; Langer, O.; Thorp, J. M.; Ramin, S. M.; Mercer, B. M.; National Institute of Child Health Human Development Maternal-Fetal Medicine Units Network; et al. (2006). "Maternal morbidity associated with multiple repeat cesarean deliveries". Obstet Gynecol. 107 (6): 1226–32. doi:10.1097/01.AOG.0000219750.79480.84. PMID   16738145. S2CID   257455.
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