What Is Placenta Accreta?

Placenta accreta is a severe obstetric complication involving an abnormally deep attachment of the placenta, through the endometrium and into the myometrium (the middle layer of the uterine wall). There are three forms of placenta accreta, distinguishable by the depth of penetration.

The placenta usually detaches from the uterine wall relatively easily, but women who encounter placenta accreta during childbirth are at great risk of haemorrhage during its removal. This commonly requires surgery to stem the bleeding and fully remove the placenta, and in severe forms can often lead to a hysterectomy or be fatal.

Placenta accreta affects approximately 1 in 533 pregnancies.

Variants

There are multiple variants, defined by the depth of their attachment to uterine wall:

Type Description Percent
placenta accreta An invasion of the myometrium which does not penetrate the entire thickness of the muscle. This form of the condition accounts for around 75% of all cases. 75-78%
placenta increta Occurs when the placenta further extends into the myometrium, penetrating the muscle. 17%
placenta percreta The worst form of the condition is 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 bladder[2]. 5-7%

Diagnosis

Placenta accreta is very rarely recognised before birth, and is very difficult to diagnose. A Doppler ultrasound can lead to the diagnosis of a suspected accreta and an MRI will give more detail leading to further suspicion of such an abnormal placenta. However, both the ultrasound and the MRI rarely confirm an accreta with certainty. While it can lead to some vaginal bleeding during the third trimester, this is more commonly associated with the factors leading to the condition. In some cases the second trimester can see elevated maternal serum alpha-fetoprotein levels, though this is also an indicator of many other conditions[3].

During birth, placenta accreta is suspected if the placenta has not been delivered within 30 minutes of the birth. Usually in this case, manual blunt dissection or placenta traction is attempted but can cause haemorrhage in accreta.

Risk factors

The condition affects around 10% of cases of placenta praevia, and 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,[4] (which is used for many indications including miscarriage, termination, and postpartum hemorrhaging), myomectomy,[5] 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.[6]

Treatment

The safest treatment is a planned caesarean section and abdominal hysterectomy if placenta accreta is diagnosed before birth.[7][8]

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.[8] Techniques include

  • leaving the placenta in the uterus
  • intrauterine balloon catheterisation to compress blood vessels
  • embolisation of pelvic vessels

If the woman decides to proceed with a vaginal delivery, blood products for transfusion should be prepared.[9]

References

  1. ^ Wu S, Kocherginsky M, Hibbard JU. Abnormal placentation: twenty-year analysis. Am J Obstet Gynecol 2005 May;192(5):1458-61.
  2. ^ Miller, David A. (2 November 2004). ‘Accreta Obstetric HemorrhageHigh Risk Pregnancy Directory at ObFocus. Accessed 25 January 2006
  3. ^ Mayes, M., Sweet, B. R. & Tiran, D. (1997). Mayes’ Midwifery – A Textbook for Midwives 12th Edition, pp. 524, 709. Baillière Tindall. ISBN 0-7020-1757-4
  4. ^ 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.
  5. ^ 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. PMID 18946102.
  6. ^ American Pregnancy Association (January 2004) ‘Placenta Accreta‘. Accessed 16 October 2006
  7. ^ 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.[page needed]
  8. ^ a b 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.
  9. ^ 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.

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