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T he placenta accreta spectrum (PAS), the classical terminology which includes placentas accreta, increta and percreta, is among the most morbid of pregnancy-related conditions. The precise pathophysiologic mechanisms that lead to PAS remain elusively incompletely defined, but the clinical consequences of PAS are clear: placental invasion and the accompanying hypervascularity involving the uterus and placenta place women with this condition at exceptional historical risk for delivery by Caesarean hysterectomy, massive hemorrhage, disseminated intravascular coagulopathy, and in the most tragic cases, death. Increasingly, for select cases focal myometrial resection with uterine repair and conservative management strategies in which the placenta is left in situ to resorb or be expelled are being used. Some women managed conservatively will still ultimately require delayed hysteroscopy or hysterectomy, and optimal patient selection for these treatment modalities has yet to be defined precisely. Interest in optimizing the diagnosis and treatment of PAS is gaining traction, and several groups of multi-disciplinary experts Received November 28, 2020, from the Baylor College of Medicine/Texas Children’s Hospital and Fetal Center, Houston, Texas, USA (K.A.F., C.I.C., W.L.); Fetal Medicine Unit, John Radcliffe Hospital, Oxford, UK (S.C.); Department of Women’s and Reproductive Health, University of Oxford, Oxford, UK (S.C.); Department of Obstetrics & Gynecology, University of Utah Health, Salt Lake City, Utah, USA (B.D.E.); Maternal Fetal Medicine, Department of Obstetrics & Gynaecology, Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada (S.R.H.); Department of Obstetrics and Gynecology, CEMIC University Hospital, Buenos Aires, Argentina (J.M.P.-J.); and Maternal-Fetal Medicine, Department of Obstetrics & Gynecology, Miller Children’s & Women’s Hospital/ Long Beach Memorial Medical Center, Long Beach, California, USA (V.K.S.). Manuscript accepted for publication February 1, 2021. Address correspondence to Karin A. Fox, MD, MEd, Department of Obstetrics and Gynecology, Baylor College of Medicine, 1 Baylor Plaza, Houston, Texas 77030.