The placenta accreta and its variants (Placenta Accreta Spectrum Disorders - PASd) represents an emerging obstetric pathology burdened by high mortality and maternal-fetal morbidity, especially when the diagnosis is not made before delivery. PAS-d includes all cases of myometrial invasion (confined to the uterus but also beyond the uterus) which, due to inadequate decidua basalis, are associated with abnormal penetration of trophoblastic tissues through the myometrium, sometimes up to the uterine serosa and beyond.

The incidence of PAS-d has increased worldwide from 1 in 2500 to 1 in 500 deliveries in recent years due to rising caesarean section rates. PAS-d have recently been classified according to the degree of invasion into: placenta accreta (abnormal adherence to the superficial layers of the myometrium), increta (deep invasion of the myometrium), and percreta (invades the uterine serosa and sometimes extends to adjacent pelvic organs); different degrees of PAS can coexist in the same patient and the accretism phenomenon can be focal or diffuse.

Prior to the advent of high-resolution ultrasonography, most of the diagnosis of PAS was made at the time of delivery, with an inability or difficulty in delivery, possible placenta retention and postpartum haemorrhage. In current obstetric practice, prenatal ultrasound, with gray-scale and color-doppler imaging, is a fundamental screening and diagnostic tool for PAS-d, which however remains today an underestimated and often undiagnosed condition before delivery.
Ultrasonographic findings of PAS-d in the second and third trimesters have been well documented; however, the diagnostic criteria still vary from study to study with heterogeneity on the terminology used and its meaning.

Current challenges include the ability to screen, diagnose PAS-d in the first trimester, as well as predict the degree and topography of placental villous invasion in the 2nd and 3rd trimester. Since these are evolutionary conditions with a high risk of maternal morbidity and mortality, serial follow-ups are necessary (starting from 24 weeks of gestation), in order to accurately predict the degree and extent of the invasion, stratify the prognosis and plan the best surgical treatment.

This app was created with the idea of providing gynaecologists with a tool that helps in the ultrasound diagnosis of PAS-d, based on the experience of operators in the sector and recent scientific evidence. The app, in fact, guides the operator in carrying out a check-list of ultrasound parameters and finally allows to quantify the risk that the pathology is present and to refer the patient to a Center with adequate resources and with high expertise in diagnostic-therapeutic procedure.