Ultrasound is sufficient for prenatal diagnosis of placenta previa accreta: a systematic review and meta-analysis

Ultrasound is highly sensitive and specific in diagnosing placenta previa accreta, after previous cesarean section when performed by skilled sonologist reports the results of a systematic review and meta-analysis by Jauniaux and Bhide published in July issue of Obstetrics and Gynecology.

Placenta accreta is a potential life-threatening condition and requires multidiscipline involvement for successful management and reducing maternal and neonatal morbidity and mortality. Because of increasing incidence of cesarean sections, the incidence of morbidly adherent placenta is on rise.

The incidence of placenta previa accreta was 4.1% in women with 1 prior cesarean and 13.3% in women with ≥2 previous cesarean deliveries.

Prenatal diagnosis of placenta accreta allows for sufficient time and planning by involving the concerned discipline to be prepared in advance.

The researchers included data from 14 cohort studies with 3889 pregnancies presenting with placenta previa or low-lying placenta and 1 or more prior cesarean deliveries in the quantitative analysis.

There were 328 (8.4%) cases of placenta previa accreta, 90% (298 cases) of which were diagnosed with ultrasound.

Two hundred and eight patients underwent cesarean hysterectomy out of 232 cases (89.7%)

The odds of diagnosing placenta accreta were higher in prospective studies (odds ratios = 228.5) as compared to retrospective studies (odds ratio=80.8). Sonography was more accurate in diagnosing placenta accreta as the depth of villous invasion increased.

The authors stressed the need of developing screening protocols for better management of this increasingly common and life threatening obstetric complication.

Placental Accreta Index (PAI) was recently proposed to predict individual risk for morbidly adherent placenta using 2-D and color Doppler sonographic exam. It includes 5 parameters: 2 or > cesarean delivery, lacunae, myometrial thickness, anterior placenta previa and bridging vessels.

Each parameter was weighted to create a 9-point scale in which a score of 0-9 provided a probability of invasion that ranged from 2–96%, respectively. The probability of invasion increases with increasing PAI score, such that a score of 9 confers a 96% chance of histologic placental invasion.

But, the score needs further validation before it can be used as a standardized method in prediction of placenta accreta, but it definitely improved the  antenatal detection.