Placenta Accreta

Placenta Accreta

Definition:
Placenta accreta is a kind of abnormal villous placental implantation in the lower spectrum of severity and associated complications, in this the placental villi extend beyond the confines of the endometrium and attach to the superficial aspect of the myometrium but without deep invasion, rather than being restricted within the decidua basalis(normal occurrence)

Epidemiology:
It is the most common form of placental invasion accounting for 75% of cases. It is thought to occur in approximately 1 in 7,000 pregnancies. The incidence is increasing due to increased practice of Caesarean sections. The combination of previous Caesarean section and an anterior placenta previa  raises strong possibility of a placenta accreta. This disease has a maternal mortality of up to 7%.

Pathogenesis:
The abnormal implantation is thought to result from a deficiency in the decidua basalis, in which the decidua is partially or completely replaced by loose connective tissue. In placenta accreta, chorionic villi and/or cytotrophoblasts directly attach to the myometrium with little or no intervening decidua.

Risk Factors:
Known Risk Factors of Placenta Accreta include;

• Placenta Previa
• Prior cesarean section
• Uterine anomalies
• Previous uterine surgery
• Dilation and curettage(D&C)
• Myomectomy
• Maternal age greater than 35 years
• Multiparity

Associated Laboratory Findings

• Elevated Levels of Alpha Feto-Protein
• Elevated Levels of Human Chorionic Gonadotrophin

Diagnosis:

When the antepartum diagnosis of placenta accreta is made, it is usually based on ultrasound findings in the second or third trimester, there are isolated case reports of placenta accreta being diagnosed in the first trimester.

Ultrasound: has been reported to have sensitivity of 89.5%, positive predictive value of 68% and negative predictive value of 98% for diagnosis of placenta accreta.
Several sonographic criteria for the diagnosis of placenta accreta have been reported:

• marked thinning or loss of the retroplacental hypoechoic zone
• interruption of the hyperechoic border between the uterine serosa and bladder
• presence of mass-like tissue with echogenicity similar to that of the placenta
• visualization of prominent vessels or lakes within the placenta or myometrium

N/B: When a placenta accreta occurs on the posterior or lateral walls of the uterus, it may be difficult to detect by ultrasound.
MRI is also valuable in the diagnosis of Placenta Accreta if ultrasound is inconclusive or if Percreta is suspected.

Treatment and Prognosis:
A definitive treatment for placenta accreta consists of a hysterectomy with possible resection of adjacent organs if percreta is present. A placenta accreta is reported to be the most common indication for emergency peripartum hysterectomy.
In certain instances, however, conservative treatment may be used, especially if uterine preservation is desired. Conservative measures include curettage, over sewing of the placental bed, and ligation of the uterine arteries or the anterior divisions of the internal iliac arteries.

Complications:
Can progress to other more severe forms like Increta