Placenta accreta

Placenta accreta is a severe obstetric complication involving an abnormal attachment of the placenta to 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 that 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 2,500 pregnancies.

Variants

The most common form of placenta accreta is an attachment onto the myometrium which does not penetrate the muscle itself. There are two further variants of the condition that are known by specific names and are defined by the depth of their attachment to uterine wall. However, this is the most common form of the condition and accounts for around 75–78% of all cases.

Placenta increta occurs when the placenta extends into the muscle of the uterine wall and happens in around 17% of all cases. Placenta percreta, the worst form of the condition and occurring in 5–7% of cases, is when the placenta penetrates the entire uterine wall. This variant can lead to the placenta attaching to other organs such as the bladder.

Diagnosis

Placenta accreta is very rarely recognised before birth, and is very difficult to diagnose. 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.

Risk factors

The condition affects around 10% of cases of placenta praevia, and is increased in incidence by the presence of scar tissue from a past 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.

References

Miller, David A. (2 November 2004). Obstetric Hemorrhage, High Risk Pregnancy Directory at ObFocus. Accessed 25 January 2006.
(January 2004). Placenta Accreta at the American Pregnancy Association
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.

External links

Placenta Accreta and Percreta: Sonographic, MRI, and Surgical Correlation at OBGYN.net
Placenta Accreta at For Parents By Parents
"Donors save mum's life" at The Herald Sun, 13 January 2006.