{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,4]],"date-time":"2026-09-04T09:37:38Z","timestamp":1788514658584,"version":"build-2803163510"},"reference-count":25,"publisher":"Wiley","issue":"5","license":[{"start":{"date-parts":[[2026,3,4]],"date-time":"2026-03-04T00:00:00Z","timestamp":1772582400000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2026,3,4]],"date-time":"2026-03-04T00:00:00Z","timestamp":1772582400000},"content-version":"tdm","delay-in-days":0,"URL":"http:\/\/doi.wiley.com\/10.1002\/tdm_license_1.1"}],"funder":[{"DOI":"10.13039\/501100009780","name":"Region Sk\u00e5ne","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100009780","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["obgyn.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Acta Obstet Gynecol Scand"],"published-print":{"date-parts":[[2026,5]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:sec>\n                    <jats:title>Introduction<\/jats:title>\n                    <jats:p>Consensus is lacking regarding the upper limit for a safe contraction frequency during labor. We aimed to assess the association between different contraction frequencies and acidemia at birth, and whether an association was affected by oxytocin augmentation, concomitant cardiotocography (CTG) classification, and stage of labor.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Material and Methods<\/jats:title>\n                    <jats:p>\n                      This is a case\u2013control study based on CTG traces from births in southern Sweden during 2012\u20132017. Cases (\n                      <jats:italic>N<\/jats:italic>\n                      \u2009=\u2009364) had umbilical artery pH &lt;7.1 if born by first\u2010stage cesarean section and pH &lt;7.05 if born vaginally or by second\u2010stage cesarean. Controls were included with a 1:2 ratio (\n                      <jats:italic>N<\/jats:italic>\n                      \u2009=\u2009728) and had pH \u22657.15. CTG traces from the hour prior to birth were assessed blinded to the clinical outcome. Logistic regression was used to estimate odds ratios (OR) with 95% confidence intervals (CI).\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      After excluding insufficient topography traces, 328 cases and 677 controls remained for analysis. Contraction frequencies 5, 5\u20136, and \u22656 per 10\u2009min occurred in 15.2%, 19.5%, and 29.6% of cases and in 15.1%, 16.5%, and 11.1% of controls, respectively. The OR (95% CI) for acidemia were 1.6 (1.1\u20132.4), 1.9 (1.3\u20132.7), and 4.3 (3.0\u20136.2), respectively, compared with a reference group of &lt;5. When comparing two separate binary cut\u2010offs of\n                      <jats:italic>&gt;5<\/jats:italic>\n                      and\u2009\n                      <jats:italic>\u22655<\/jats:italic>\n                      contractions, similar strengths of association with acidemia were demonstrated with OR 2.7 (2.1\u20133.6) and 2.5 (1.9\u20133.3), respectively. The effect of contraction frequency &gt;5 was similar in spontaneous (\n                      <jats:italic>n<\/jats:italic>\n                      \u2009=\u2009586) and oxytocin\u2010augmented (\n                      <jats:italic>n<\/jats:italic>\n                      \u2009=\u2009419) labor (OR 2.5, 1.7\u20133.8 vs. OR 2.4, 1.6\u20133.6), and whether the CTG was normal, suspicious, or pathological according to the Swedish CTG template (OR 2.1, 1.3\u20133.3; OR 3.5, 1.6\u20137.6; and OR 2.6, 1.4\u20134.7, respectively). The study lacked power to study any association during the first stage of labor.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>Increasing contraction frequency is incrementally associated with fetal acidemia. Although an increased risk of acidosis is evident at contraction frequencies as low as five, such frequencies are common while acidemia is uncommon, implying a poor positive predictive value. A contraction frequency of more than five is associated with acidemia in both spontaneous and oxytocin\u2010augmented labor, and even when the fetal heart trace is normal.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1111\/aogs.70181","type":"journal-article","created":{"date-parts":[[2026,3,8]],"date-time":"2026-03-08T14:11:47Z","timestamp":1772979107000},"page":"904-911","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Contraction frequency and acidemia at birth: A case\u2013control study"],"prefix":"10.1111","volume":"105","author":[{"given":"Johanna Wagner","family":"Bjurstr\u00f6m","sequence":"first","affiliation":[{"name":"Department of Clinical Sciences Lund University  Lund Sweden"},{"name":"Department of Obstetrics and Gynecology Holb\u00e6k Hospital  Holb\u00e6k Denmark"},{"name":"Department of Clinical Medicine, Faculty of Health and Medical Sciences University of Copenhagen  Copenhagen 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