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      Incidence, risk factors and perinatal outcomes for placenta accreta in Australia and New Zealand: a case–control study

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          Estimate the incidence of placenta accreta and describe risk factors, clinical practice and perinatal outcomes.


          Case–control study.


          Sites in Australia and New Zealand with at least 50 births per year.


          Cases were women giving birth (≥20 weeks or fetus ≥400 g) who were diagnosed with placenta accreta by antenatal imaging, at operation or by pathology specimens between 2010 and 2012. Controls were two births immediately prior to a case. A total of 295 cases were included and 570 controls.


          Data were collected using the Australasian Maternity Outcomes Surveillance System.

          Primary and secondary outcome measures

          Incidence, risk factors (eg, prior caesarean section (CS), maternal age) and clinical outcomes of placenta accreta (eg CS, hysterectomy and death).


          The incidence of placenta accreta was 44.2/100 000 women giving birth (95% CI 39.4 to 49.5); however, this may overestimated due to the case definition used. In primiparous women, an increased odds of placenta accreta was observed in older women (adjusted OR (AOR) women≥40 vs <30: 19.1, 95% CI 4.6 to 80.3) and current multiple birth (AOR: 6.1, 95% CI 1.1 to 34.1). In multiparous women, independent risk factors were prior CS (AOR ≥2 prior sections vs 0: 13.8, 95% CI 7.4 to 26.1) and current placenta praevia (AOR: 36.3, 95% CI 14.0 to 93.7). There were two maternal deaths (case fatality rate 0.7%).

          Women with placenta accreta were more likely to have a caesarean section (AOR: 4.6, 95% CI 2.7 to 7.6) to be admitted to the intensive care unit (ICU)/high dependency unit (AOR: 46.1, 95% CI 22.3 to 95.4) and to have a hysterectomy (AOR: 209.0, 95% CI 19.9 to 875.0). Babies born to women with placenta accreta were more likely to be preterm, be admitted to neonatal ICU and require resuscitation.

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          Most cited references 31

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          Maternal morbidity associated with multiple repeat cesarean deliveries.

          Although repeat cesarean deliveries often are associated with serious morbidity, they account for only a portion of abdominal deliveries and are overlooked when evaluating morbidity. Our objective was to estimate the magnitude of increased maternal morbidity associated with increasing number of cesarean deliveries. Prospective observational cohort of 30,132 women who had cesarean delivery without labor in 19 academic centers over 4 years (1999-2002). There were 6,201 first (primary), 15,808 second, 6,324 third, 1,452 fourth, 258 fifth, and 89 sixth or more cesarean deliveries. The risks of placenta accreta, cystotomy, bowel injury, ureteral injury, and ileus, the need for postoperative ventilation, intensive care unit admission, hysterectomy, and blood transfusion requiring 4 or more units, and the duration of operative time and hospital stay significantly increased with increasing number of cesarean deliveries. Placenta accreta was present in 15 (0.24%), 49 (0.31%), 36 (0.57%), 31 (2.13%), 6 (2.33%), and 6 (6.74%) women undergoing their first, second, third, fourth, fifth, and sixth or more cesarean deliveries, respectively. Hysterectomy was required in 40 (0.65%) first, 67 (0.42%) second, 57 (0.90%) third, 35 (2.41%) fourth, 9 (3.49%) fifth, and 8 (8.99%) sixth or more cesarean deliveries. In the 723 women with previa, the risk for placenta accreta was 3%, 11%, 40%, 61%, and 67% for first, second, third, fourth, and fifth or more repeat cesarean deliveries, respectively. Because serious maternal morbidity increases progressively with increasing number of cesarean deliveries, the number of intended pregnancies should be considered during counseling regarding elective repeat cesarean operation versus a trial of labor and when debating the merits of elective primary cesarean delivery. II-2.
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            Abnormal placentation: twenty-year analysis.

            This study was undertaken to determine whether the rate of abnormal placentation is increasing in conjunction with the cesarean rate and to evaluate incidence, risk factors, and outcomes. Cases from 1982-2002 were identified by histopathologic or strong clinical criteria. Risk factors were assessed in a matched case-control study, and analyzed using conditional logistic regression models. There were 64,359 deliveries, with cesarean rates increasing from 12.5% (1982) to 23.5% (2002). The overall incidence of placenta accreta was 1 in 533. Significant risk factors for placenta accreta in our final analysis included advancing maternal age (odds ratio [OR] 1.13, 95% CI 1.089-1.194, P < .0001), 2 or more cesarean deliveries (OR 8.6, 95% CI 3.536-21.078, P < .0001), and previa (OR 51.4, 95% CI: 10.646-248.390, P < .0001). The rate of placenta accreta increased in conjunction with cesarean deliveries; the most important risk factors were previous cesarean delivery, previa, and advanced maternal age.
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              Clinical risk factors for placenta previa-placenta accreta.

              Our purpose was to define the clinical risk factors associated with placenta previa-placenta accreta. Hospital records were reviewed of all cases of placenta accreta confirmed histologically between January 1985 and December 1994. Additionally, we reviewed the records of all women with placenta previa and all those undergoing cesarean hysterectomy during the same period. Multiple logistic regression analysis was used to identify independent clinical risk factors for placenta accreta. Among 155,670 deliveries, 62 (1/2510) were complicated by histologically confirmed placenta accreta. Placenta accreta occurred in 55 of 590 (9.3%) women with placenta previa and in 7 of 155,080 (1/22,154) without placenta previa (relative risk 2065, 95% confidence interval 944 to 4516, p or = 35 years) and previous cesarean delivery were independent risk factors for placenta accreta. Placenta accreta was present in 36 of 124 (29%) cases in which the placenta was implanted over the uterine scar and in 4 of 62 (6.5%) cases in which it was not (relative risk 4.5, 95% confidence interval 1.68 to 12.07). Among women with placenta previa, the risk of placenta accreta ranged from 2% in women < 35 years old with no previous cesarean deliveries to almost 39% in women with two or more previous cesarean deliveries and an anterior or central placenta previa. Placenta accreta occurs in approximately 1 of 2500 deliveries. Among women with placenta previa, the incidence is nearly 10%. In this high-risk group advanced maternal age and previous cesarean section are independent risk factors.

                Author and article information

                BMJ Open
                BMJ Open
                BMJ Open
                BMJ Publishing Group (BMA House, Tavistock Square, London, WC1H 9JR )
                5 October 2017
                : 7
                : 10
                [1 ] departmentDepartment of Obstetrics and Gynaecology , University of Auckland , Auckland, New Zealand
                [2 ] departmentAustralian Centre for Public and Population Health Research, Faculty of Health , University of Technology Sydney , Sydney, New South Wales, Australia
                [3 ] departmentDepartment of National Women’s Health , Auckland City Hospital , Auckland, New Zealand
                [4 ] departmentDepartment of Nursing, Melbourne School of Health Sciences , The University of Melbourne and School of Nursing and Midwifery , Melbourne, Australia
                [5 ] departmentDepartment of ANU Medical School , Australian National University , Canberra, Australia
                [6 ] departmentSchool of Medicine , Griffith University , Gold Coast, Queensland, Australia
                [7 ] National Perinatal Epidemiology Unit , Oxford, UK
                Author notes
                [Correspondence to ] and Dr Cynthia M Farquhar; c.farquhar@
                © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

                This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:

                Funded by: FundRef, National Health and Medical Research Council;
                Funded by: Perinatal and Maternal Mortality Review Committee;
                Obstetrics and Gynaecology
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                caesarean, c-section, placenta accreta, placentation


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