Placenta accreta

Placenta accreta
Classification and external resources
Types of placenta accreta
ICD-10	O73.0
ICD-9	667.0
DiseasesDB	10091

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 2,500 pregnancies.

Variants

The most common form of placenta accreta is an invasion of the myometrium which does not penetrate the entire thickness of the muscle. This form of the condition accounts for around 75-78% of all cases, and has no name other than placenta accreta.

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. Placenta increta occurs when the placenta further extends into the myometrium 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 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^[1].

Diagnosis

Placenta accreta is very rarely recognised before birth, and is very difficult to diagnose. An 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 as 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^[2].

Risk factors

The condition affects around 10% of cases of placenta praevia, and is increased in incidence by the presence of scar tissue ie Asherman's syndrome usually from past uterine surgery, especially from a past D&C,^[3] (which is used for many indications including miscarriage, termination, and postpartum hemorrhaging), myometcomy ^[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].

References

External links

• 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