{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,11,13]],"date-time":"2026-11-13T14:13:04Z","timestamp":1794579184834,"version":"4.9.1"},"reference-count":35,"publisher":"Wiley","issue":"12","license":[{"start":{"date-parts":[[2025,7,14]],"date-time":"2025-07-14T00:00:00Z","timestamp":1752451200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"funder":[{"DOI":"10.13039\/501100004257","name":"Helse Vest","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100004257","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000066","name":"National Institute of Environmental Health Sciences","doi-asserted-by":"publisher","id":[{"id":"10.13039\/100000066","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["obgyn.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["BJOG"],"published-print":{"date-parts":[[2025,11]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                  <jats:sec>\n                    <jats:title>Objective<\/jats:title>\n                    <jats:p>Ten to fifteen per cent has been proposed for many decades as the optimal level of caesarean section, with little supporting data. Norway provides a natural experiment in which local variations in the use of caesarean section can be related to health outcomes in the context of free access to high\u2010quality medical services.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Design<\/jats:title>\n                    <jats:p>Prospective national cohort.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Setting<\/jats:title>\n                    <jats:p>Norway.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Population<\/jats:title>\n                    <jats:p>Norwegian deliveries 1995\u20132014.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>We calculated annual rates of caesarean delivery and health outcomes for 435 municipalities. To avoid hospital referral bias, the mother's municipality of residence was the unit of analysis. Caesarean\u2010delivery rates in each year were based on the 2\u2009years before and after, avoiding indication bias. Analyses were adjusted for year, with additional adjustments in sensitivity analyses.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Main Outcome Measures<\/jats:title>\n                    <jats:p>Maternal mortality, severe maternal haemorrhage and perineal tears; stillbirth and neonatal death, neonatal encephalopathy and cerebral palsy.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>There were 1\u2009172\u2009546 deliveries across 8647 municipality\u2010year combinations over a 20\u2010year period. Caesarean rates across municipalities ranged from about 10% to 20%, with quartile values of 13%, 16% (median) and 18%. Most adverse outcomes were least frequent in municipalities with caesarean rates above 15%. Lower rates of caesarean delivery were associated with more frequent occurrence of perineal tears (OR 1.41, 95% confidence interval 1.36\u20131.46), neonatal encephalopathy (OR 1.91, 1.71\u20132.13), cerebral palsy (1.48, 1.24\u20131.77) and stillbirths (OR 1.07, 0.99\u20131.17), but also with less frequent maternal haemorrhage (OR 0.81, 0.77\u20130.85). Further adjustments had minimal effect on estimates.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>In Norway, a country with free access to high\u2010quality medical care, a local caesarean\u2010delivery rate of 10% was associated with nearly a two\u2010fold risk of neonatal encephalopathy and a 50% higher occurrence of cerebral palsy compared with areas with a caesarean\u2010delivery rate of 20%.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1111\/1471-0528.18301","type":"journal-article","created":{"date-parts":[[2025,7,14]],"date-time":"2025-07-14T08:24:17Z","timestamp":1752481457000},"page":"1781-1788","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["What Is the Safest Population\u2010Level Caesarean Delivery Rate? A National Cohort Study Using Natural Variation"],"prefix":"10.1111","volume":"132","author":[{"given":"Dag","family":"Moster","sequence":"first","affiliation":[{"name":"Department of Global Public Health and Primary Care University of Bergen  Bergen Norway"},{"name":"Department of Pediatrics Haukeland University Hospital  Bergen Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Allen J.","family":"Wilcox","sequence":"additional","affiliation":[{"name":"Epidemiology Branch (Emeritus Investigator), National Institute of Environmental Health Sciences National Institutes of Health  Durham North Carolina USA"},{"name":"Center for Fertility and Health Norwegian Institute of Public Health  Oslo Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6287-4051","authenticated-orcid":false,"given":"Rolv Terje","family":"Lie","sequence":"additional","affiliation":[{"name":"Department of Global Public Health and Primary Care 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