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.
