Placenta Accreta Syndrome

Robert Silver

• Publisher: CRC Press
• Year: 2017
• eBook ISBN: 9781498746007
• Edition: 1
• Topic: Medicine
• Subtopic: Gynecology, Obstetrics & Midwifery

Placenta accreta comprises a spectrum of disorders where all or part of the placenta becomes attached to the muscular wall of the uterus, which can result in life-threatening hemorrhage at the time of delivery. Previous surgical procedures (including cesarean delivery) and placenta previa are important risk factors, and the incidence is dramatically increasing. This important practical guide to how clinicians should diagnose and manage placenta accreta will be an invaluable reference for all obstetricians and maternal-fetal specialists.

1

Placenta Accreta: Epidemiology and Risk Factors

Daniela Carusi

CONTENTS

Definition

Incidence

Mortality

Risk Factors

Placenta Previa

Prior Cesarean Section

Maternal Age

Other Uterine Surgery

Past Obstetric History

Current Pregnancy Factors

Abnormal Endometrium

In Vitro Fertilization

Conclusions

References

Placenta accreta represents one of the most morbid conditions in modern obstetrics, with high rates of hemorrhage, hysterectomy, and intensive care unit admission.¹ By most accounts, placenta accreta appears to be on the rise,^2–4 paralleling the rise in cesarean section rate as a major risk factor. In fact, the true incidence of placenta accreta is difficult to determine, owing to marked variation in the definition of accreta and heterogeneity in the populations studied. This chapter interprets available data on incidence, mortality, and risk factors for placenta accreta.

Definition

Placenta accreta is strictly defined as direct attachment of the placental trophoblast to the uterine myometrium, with no normal intervening decidua or basalis layer.⁵ Cases with partial or complete invasion of trophoblast through the uterine wall are called increta and percreta, respectively, though all three categories are collectively identified as “accreta” in the epidemiologic literature. The definition has been further categorized based on the amount of placenta involved, with a “total” accreta involving the entire placenta, while “partial” or “focal” accretas involve individual cotyledons or areas within a cotyledon, respectively.⁶

The first published review of accreta focused on clinical rather than pathologic diagnosis, specifying “undue adherence of the placenta” to the uterine wall.⁵ More recently, the term “morbidly adherent placenta” has been used to define accreta clinically, though exact diagnostic criteria still vary from study to study. Most researchers using a clinical definition identify “difficult,” or “piecemeal” removal of the placenta,^7–10 sometimes specifying an antecedent prolonged third stage of labor following a vaginal delivery.¹¹ Some also specify placental bed hemorrhage after a difficult removal,^3,8,9 though not all authors require a morbidity factor in the diagnosis. Others have allowed a very broad clinical definition, including any postpartum curettage for retained products of conception.⁷

Concerns over diagnostic specificity have led some authors to require histologic confirmation, excluding cases that were suspected clinically but lacked pathologic evidence.^12,13 However, reliable pathologic results may not be available when the uterus is conserved, or when multicenter or national-level data are collected.^14–16 Some have conversely emphasized a clinical definition, arguing that adherence and morbidity are the most relevant features of accreta.⁶ In fact, some studies have shown that microscopic findings of accreta have a clinical correlation only 11%–33% of the time, suggesting that isolated histologic criteria may also be nonspecific.^17,18 To date, no universal, strict definition exists for data collection purposes.

Incidence

Accreta incidence estimates will be influenced both by the definition used and the specific population of patients studied. Table 1.1 details various estimates according to these factors. When using either a clinical or pathologic diagnosis, regardless of previa status or mode of delivery, general incidence ranges from 1/533 to 1/731 deliveries.^9,13,14

TABLE 1.1

Studies Reporting Accreta Incidence

Study and Years Investigated	Accreta Incidence	Patient Source	Definition	Notes
Hospital-Level Data Collection
Clark et al.^19: 1977–1983	All deliveries: 1/3372 Previas only: 1/10	Single teaching hospital, United States	Not given	Accreta diagnosed only with previa
Miller et al.^12: 1985–1994	All deliveries: 1/2510 Previas only: 1/11 Prior CS only: 1/396	Single teaching hospital, United States	All histologically confirmed	Accretas diagnosed either with previa or with hysterectomy
Zaki et al.^20: 1990–1996	All deliveries: 1/1922 Previas only: 1/9	Single hospital, Saudi Arabia	Clinical	Accreta diagnosed only with previa
Gielchinsky et al.^7: 1990–2000	All deliveries: 1/111 Previas only: 1/10	Single hospital, Israel	Clinical or histologic	Used broad clinical criteria, including ultrasound findings of RPOC requiring curettage
Wu et al.^9: 1982–2002	All deliveries: 1/533	Single teaching hospital, United States	Clinical or histologic	Excluded women with fbroids; gravida 1 patients excluded from risk factor analysis
Silver et al.^10: 1999–2002	Unlabored CS only: 1/211 Primary unlabored CS only: 1/333	19 academic centers, United States	Clinical or histologic	Evaluated unlabored CSs only
Usta et al.^8: 1983–2003	Previas only: 1/16	Single teaching hospital, Lebanon	Clinical or histologic	Included cases of previa only
Morlando et al.^3: 1976–2008	All deliveries: 1976–1978: 1/833 2006–2008: 1/322	Single teaching hospital, Italy	Clinical or histologic	Rising CS rate over time period: 17%–64%
Esh-Broder et al.^13: 2004–2009	All deliveries: 1/599	Single teaching hospital, Israel	Clinical and histologic	Searched all pathology reports
Eshkoli et al.^21: 1988–2011	Singleton CS only: 1/250	Single tertiary center, Israel	Clinical	Included singleton cesarean deliveries only
Bailit et al.^14: 2008–2011	All deliveries: 1/731	25 hospitals (22/25 teaching hospitals), United States	Clinical	Evaluated a random sample of deliveries during the time period
National-Level Data Collection
Upson et al.^16: 2005–2010	All deliveries: 1/1136 2005: 1/1266 2010: 1/943	National discharge data, Ireland	Discharge coding	ICD-10 codes for MAP and some form of accreta
Mehrabadi et al.^22: 2009–2010	All deliveries: 1/694	National coding, Canadian Institute for Health Information	Canadian Health System ICD coding	Used unique codes for accreta
Fitzpatrick et al.^23: 2010–2011	All deliveries: 1/5882 No prior CS: 1/33,000 Previa and prior CS: 1/20	National,...

Table of contents

• Cover
• Half Title
• Series Title
• Title Page
• Copyright Page
• Table of Contents
• Preface
• Contributors
• 1.   Placenta Accreta: Epidemiology and Risk Factors
• 2.   Pathophysiology of Accreta
• 3.   Ultrasound Diagnosis of the Morbidly Adherent Placenta
• 4.   MRI Diagnosis of Accreta
• 5.   Optimal Timing of Delivery of Placenta Accreta
• 6.   Surgical Management of Placenta Accreta
• 7.   Conservative Management of Placenta Accreta
• 8.   Role of Interventional Radiology in the Management of Abnormal Placentation
• 9.   Center of Excellence for Morbidly Adherent Placenta
• 10. Blood Management for Patients with Placenta Accreta
• 11. Anesthetic Considerations for Placenta Accreta
• Index