Placenta accreta, increta, and percreta: A team-based approach starts with prevention (Part 1)

Key Points

Part 1

About 3 out of every 100,000 American women who give birth to a live baby die, according to our most recent statistics (2004).¹ This figure has remained relatively unchanged since 1982 for at least three reasons: placenta accreta, placenta increta, and placenta percreta, all of which have been strongly linked to previous uterine surgery, including cesarean delivery (CD).

A patient with this complication is at increased risk for uncontrolled hemorrhage, with many women with placenta accreta/percreta losing more than 3,000 mL of blood at delivery. Clearly, clinical and surgical management should focus on prevention and treatment of uncontrolled hemorrhage.² When placenta accreta/increta/percreta is suspected before delivery, planning should involve a multidisciplinary approach, ideally within a center equipped with the needed resources. A coordinated approach may improve peripartum management and patient outcomes.

Risks factors include prior CD, placenta previa

The three types of abnormal attachment of the placenta to and through the uterine wall are defined by the degree of trophoblastic invasion on histologic examination.

1. Placenta accreta is characterized by superficial attachment of trophoblastic villi to the myometrium,

2. Placenta increta is invasion of villi into the myometrium, and

3. Placenta percreta is characterized by full penetration through the myometrial wall, with possible invasion into adjacent structures.

Abnormal placental attachment has been correlated with the absence of both the decidua basalis and Nitabuch's layer.³ Factors linked with placenta accreta include multiparity, prior uterine surgery including CD, advanced maternal age, placenta previa, and prior uterine curettage.^3-5

Placenta percreta has also been associated with endometrial ablation and reported to occur with abdominal radiation therapy, leading to thinning of the myometrium.⁶

The incidence of placenta accreta has climbed from 1:2,510 in the 1980s to 1:533 in 2002, and 1:210 in 2006, an increase that's likely related to rising CD rates over the same period.^4,7,8 Several studies have found a direct relationship between the number of prior uterine incisions and subsequent placenta accreta. After one prior CD, a woman is twice as likely to develop placenta accreta.⁴ In a recent National Institute of Child Health and Human Development (NICHD) Maternal-Fetal Medicine Units (MFMU) network study evaluating more than 30,000 CDs, women with four or more CDs had a ninefold to 30-fold increased risk of placenta accreta.^9,10

In the presence of placenta previa and multiple CDs, the risk of accreta increases by 67%.⁵ If a patient with placenta previa has had one prior CD, the risk of accreta increases to almost 25%. With placenta previa and a history of two or three C/S deliveries, this risk jumps to roughly 40% to 60%^5,9 and peaks at 70% for women who have had four or more C/S deliveries.⁵