Placenta accreta spectrum: imaging and diagnosis

Key content Antenatal imaging is a screening tool integral to ensuring women are cared for in the most appropriate setting. The pretest probability of PAS should be considered before any imaging is performed. PAS is an iatrogenic disease. Any process which disrupts the endometrium increases the risk. Caesarean birth is the most common cause. Specialist placental assessment in asymptomatic women should be offered between 24 and 28 weeks. Ultrasound and MRI have similar diagnostic value, and MRI should only be used as an adjunct following ultrasound assessment by a specialist in placental imaging. Learning objectives To understand the pathophysiology of PAS. To understand the distinction between screening for and diagnosis of PAS. To increase confidence in the interpretation of sonographic features of PAS. To provide a rationale for PAS care being provided in centres of excellence. Ethical issues If women increasingly prefer caesarean section over vaginal birth, it is likely that this trend will result in increasing numbers of complex caesarean deliveries and PAS cases. Many studies have shown decreased morbidity and mortality if PAS cases are managed by an experienced multi‐disciplinary team (MDT) in a PAS centre of excellence; therefore, accurate screening and timely referral are vital to improve patient care for women with risk factors.