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.
There are multiple variants, defined by the depth of their attachment to uterine wall:
|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.||5-7%|
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.
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.
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, (which is used for many indications including miscarriage, termination, and postpartum hemorrhaging), myomectomy, 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.
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. 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.
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- ^ 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.
- Placenta Accreta and Percreta: Sonographic, MRI, and Surgical Correlation at OBGYN.net
- Placenta Accreta at ForParentsByParents.com
- Placenta Accreta Diagnosis and Management at Expecting-Mums.com