Objective The objective was to investigate prevalence, estimate risk factors, and antenatal suspicion of abnormally invasive placenta (AIP) associated with laparotomy in women in the Nordic countries.Design Population-based cohort study.Setting and population A 3-year Nordic collaboration among obstetricians to identify and report on uterine rupture, peripartum hysterectomy, excessive blood loss, and AIP from 2009 to 2012 The Nordic Obstetric Surveillance Study (NOSS).Methods In the NOSS study, clinicians reported AIP cases from maternity wards and the data were validated against National health registries.Main outcome measures Prevalence, risk factors, antenatal suspicion, birth complications, and risk estimations using aggregated national data.Results A total of 205 cases of AIP in association with laparotomy were identified, representing 3.4 per 10 000 deliveries. The single most important risk factor, which was reported in 49% of all cases of AIP, was placenta praevia. The risk of AIP increased seven-fold after one prior caesarean section (CS) to 56-fold after three or more CS. Prior postpartum haemorrhage was associated with six-fold increased risk of AIP (95% confidence interval 3.7-10.9). Approximately 70% of all cases were not diagnosed antepartum. Of these, 39% had prior CS and 33% had placenta praevia. ConclusionOur findings indicate that a lower CS rate in the population may be the most effective way to lower the incidence of AIP. Focused ultrasound assessment of women at high risk will likely strengthen antenatal suspicion. Prior PPH is a novel risk factor associated with an increased prevalence of AIP.Keywords Incidence, placenta accreta, prenatal diagnosis, risk factors.Tweetable abstract An ultrasound assessment in women with placenta praevia or prior CS may double the awareness for AIP.

The Nordic medical birth registers have long been used for valuable clinical research. Their collection of data for more than four decades offers unusual possibilities for research across generations. At the same time, serum and blotting paper blood samples have been stored from most neonates. Two large cohorts (approximately 100 000 births) in Denmark and Norway have been described by questionnaires, interviews and collection of biological samples (blood, urine and milk teeth), as well as a systematic prospective follow-up of the offspring. National patient registers provide information on preceding, underlying and present health problems of the parents and their offspring. Researchers may, with permission from the national authorities, obtain access to individualized or anonymized data from the registers and tissue-banks. These data allow for multivariate analyses but their usefulness depends on knowledge of the specific registers and biological sample banks and on proper validation of the registers.

The increased total cesarean rates in the Nordic countries are explained by increased cesarean rates among nulliparous women, and by an increased percentage of women with previous cesarean. Meanwhile, induction rates on nulliparous increased significantly, but the impact on the total cesarean rate was unclear. The Robson classification facilitates benchmarking and targeting efforts for lowering the cesarean rates.

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The Nordic Obstetric Surveillance Study: a study of complete uterine rupture, abnormally invasive placenta, peripartum hysterectomy, and severe blood loss at delivery Colmorn, Lotte B.; Petersen, Kathrine B.; Jakobsson, Maija; Lindqvist, Pelle G.; Klungsoyr, Kari; Källén, Karin; Bjarnadottir, Ragnheidur I.; Tapper, Anna-Maija; Bordahl, Per E.; Gottvall, Karin; Thurn, Lars; Gissler, Mika; Krebs, Lone; Langhoff-Roos, Jens Link to publication Citation for published version (APA): Colmorn, L. B., Petersen, K. B., Jakobsson, M., Lindqvist, P. G., Klungsoyr, K., Källén, K., ... Langhoff-Roos, J. (2015). The Nordic Obstetric Surveillance Study: a study of complete uterine rupture, abnormally invasive placenta, peripartum hysterectomy, and severe blood loss at delivery. Acta Obstetricia et Gynecologica Scandinavica, 94(7), 734-744. DOI: 10.1111/aogs.12639 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal AOGS MAIN RESEARCH ARTICLEThe Nordic Obstetric Surveillance Study: a study of complete uterine rupture, abnormally invasive placenta, peripartum hysterectomy, and severe blood loss at delivery AbstractObjective. To assess the rates and characteristics of women with complete uterine rupture, abnormally invasive placenta, peripartum hysterectomy, and severe blood loss at delivery in the Nordic countries. Design. Prospective, Nordic collaboration. Setting. The Nordic Obstetric Surveillance Study (NOSS) collected cases of severe obstetric complications in the Nordic countries from April 2009 to August 2012. Sample and methods. Cases were reported by clinicians at the Nordic maternity units and retrieved from medical birth registers, hospital discharge registers, and transfusion databases by using International Classification of Diseases, 10th revision codes on diagnoses and the Nordic Medico-Statistical Committee Classification of Surgical Procedure codes. Main outcome measures. Rates of the studied complications and possible risk factors among parturients in the Nordic countries. Results. The studied complications were reported in 1019 instances among 605 362 deliveries during the study period. The reported rate of severe blood loss at delivery was 11.6/10 000 deliveries, complete uterine rupture was 5.6/10 000 deliveries, abnormally invasive placenta was 4.6/10 000 deliveries, and peripartum hysterectomy was 3.5/10 000 deliveries. Of the women, 25% had two or more complications. Women with complications were more often >35 years old, overweight, with a higher parity, a...

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A combination of prospective data collected from clinicians and information gathered from register-based databases can yield valuable data, improving the registration accuracy for rare, near-miss cases. However, proper and uniform clinical guidelines for the use of well-defined international diagnostic codes are still needed.