The new world of placenta accreta spectrum disorders

A PubMed (www.ncbi.nlm.nih.gov/pubmed) search of the term "placenta accreta" at the time of writing of this editorial generated 2296 hits, including 147 for the year 2017 up to December 1, and 138 for the entire of 2016. Both years record more publications on placenta accreta than the entire period between 1947 and 1962. There are two different main categories of placenta accreta: the abnormally adherent placenta (placenta creta) and the abnormally invasive placenta. The latter category is divided between placenta increta and placenta percreta depending on the depth of penetration of the villous tissue into the uterine myometrium. As many articles do not differentiate between the two categories and/or do not provide detailed data on histopathology, to be inclusive we have opted to use the term placenta accreta spectrum (PAS) disorders throughout this special themed issue of the International Journal of Gynecology and Obstetrics. The first case of placenta accreta listed on PubMed was reported in 1927 by Dr D.S. Forster, a scholar in gynecology at the Pathology Department of the Montreal General Hospital, Montreal, Canada.1 This case, for which a hysterectomy had to be performed, was the only one recorded out of 8000 deliveries (0.013%) during a 6-year survey at the Montreal General Hospital. This case predates by a decade the now "classical" cohort study of 18 cases published by Irving and Hertig,2 who calculated the prevalence of placenta accreta to be 1 in 1956 deliveries (0.12%) in their study population at the Boston Lying-in Hospital, and 1 in 30 000 deliveries in the USA. Eight decades later, the prevalence of PAS disorders has jumped to around 1 in 500 (0.2%) deliveries in most high- and middle-income countries.3 In some cases, the high incidence of PAS disorders could be due to over diagnosis, secondary to the inclusion of cases of placental retention in many cohort studies.4 This may also have been the case in the study by Irving and Hertig since none of their cases had villous tissue penetrating the myometrium on microscopic examination.2 The distribution of risk factors and grades of PAS disorders has also completely changed from the 1930s. The case described by Forster was a case of placenta increta following a curettage during a second birth and manual removal of the placenta during a third delivery.1 Only one of the 20 cases personally treated by Irving and Hertig occurred after a previous cesarean delivery.2 Predisposing factors for PAS disorders in subsequent pregnancies until the 1950s were manual removal of the placenta and/or "vigorous" uterine curettage during a prior delivery. Today, around 95% of women presenting with a PAS disorder at delivery have had at least one previous cesarean delivery and the most common presentation is a placenta previa accreta.5 Moreover, there is strong evidence that the incidence of PAS disorders increases with the number of previous cesarean deliveries.6 Similarly, the ratio of adherent/invasive accreta placentas has changed from 70/30 in the 1970s to 50/50 in the last two decades3—a change that can be linked to the increase in the number of grand multiparous women with multiple cesarean scars allowing for deeper and extended villous invasion in subsequent pregnancies. Accreta placentation is now almost an entirely iatrogenic condition. With the continuous rise in cesarean delivery rates in most countries around the world, both the prevalence and incidence of PAS disorders will continue to increase. PAS disorders have become a leading cause of peripartum hysterectomy, maternal morbidity, and even mortality. The development of FIGO consensus guidelines on PAS disorders and a themed issue on this topic in a specialist international journal are timely. Both the FIGO guidelines and the peer-reviewed articles included in this issue address various aspects of the epidemiology, diagnosis, and conservative and surgical management of PAS disorders, and should provide readers with a comprehensive overview of this complex disorder. Recent progress has been made in standardizing the clinical and ultrasound diagnosis of PAS disorders,3, 4 but there is still need for authors to use inclusive terminology and to include detailed histopathologic data when possible. Within this context, multicenter prospective studies are essential to improve the perinatal management of PAS disorders. We hope that this themed issue will promote such collaborations at both the national and international level. EJ drafted the manuscript. All authors were involved in the critical discussion and approved the final version for publication. EJ is the guarantor of the article. The authors have no conflicts of interest.

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