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The study assigned the outcomes of preterm birth and SGA by each method among participants with complete gestational age information (\n                      <jats:italic>N<\/jats:italic>\n                      \u2009=\u2009392). The study reported unadjusted prevalence differences (PDs) and 95% confidence intervals (CIs) for preterm birth and SGA, by each method, with two commonly measured maternal characteristics: age\u2009\u2265\u200935\u2009years (versus &lt;\u200935) and body mass index \u2265\u200925\u2009kg\/m\n                      <jats:sup>2<\/jats:sup>\n                      (versus &lt;\u200925), and with aspirin treatment (versus placebo).\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>For all but one characteristic\u2010outcome pair examined, unadjusted PDs were similar, within 3 percentage points, for all gestational age measurement techniques. The largest discrepancy among the PDs was in the association of age \u2265\u200935\u2009years with preterm birth: PD\u2009=\u20096% (95% CI: \u22126, 17) when defined by ovulation, 1% (95% CI: \u221210, 11) by ultrasound, and 2% (95% CI: \u22128, 11) by LMP. Precision of the PDs, as assessed by their confidence limit differences, did not identify a consistently more precise gestational age measurement technique.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>Even when gestational age was measured prospectively and early in pregnancy, small differences in the classification of preterm birth and SGA were found. These differences have the potential to bias the association of maternal characteristics with these outcomes. This should be considered by researchers, particularly in populations where the gestational age assignment technique is unknown.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1111\/ppe.70135","type":"journal-article","created":{"date-parts":[[2026,5,28]],"date-time":"2026-05-28T13:55:34Z","timestamp":1779976534000},"page":"465-470","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Influence of Gestational Age Measurement Technique on the Associations Between Maternal Characteristics and Birth Outcomes"],"prefix":"10.1111","volume":"40","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-5795-9763","authenticated-orcid":false,"given":"Ginna L.","family":"Doss","sequence":"first","affiliation":[{"name":"Epidemiology Branch National Institute of Environmental Health Sciences (NIEHS), National Institutes of Health (NIH), Department of Health and Human Services (DHHS)  North Carolina USA"},{"name":"Department of Epidemiology Gillings School of Global Public Health, University of North Carolina  North Carolina USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Julie L.","family":"Daniels","sequence":"additional","affiliation":[{"name":"Department of Epidemiology Gillings School of Global Public Health, University of North Carolina  North Carolina USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0133-3176","authenticated-orcid":false,"given":"Sunni L.","family":"Mumford","sequence":"additional","affiliation":[{"name":"Department of Biostatistics, Epidemiology, and Informatics Perelman School of Medicine, University of Pennsylvania  Philadelphia Pennsylvania USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Charles","family":"Poole","sequence":"additional","affiliation":[{"name":"Department of Epidemiology Gillings School of Global Public Health, University of North Carolina  North Carolina USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Anne Z.","family":"Steiner","sequence":"additional","affiliation":[{"name":"Department of Obstetrics and Gynecology University of North Carolina School of Medicine  North Carolina USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3757-641X","authenticated-orcid":false,"given":"Enrique F.","family":"Schisterman","sequence":"additional","affiliation":[{"name":"Department of Biostatistics, Epidemiology, and Informatics Perelman School of Medicine, University of Pennsylvania  Philadelphia Pennsylvania USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Robert M.","family":"Silver","sequence":"additional","affiliation":[{"name":"Department of Obstetrics and Gynecology University of Utah School of Medicine  Salt Lake City Utah USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Anne Marie Z.","family":"Jukic","sequence":"additional","affiliation":[{"name":"Epidemiology Branch National Institute of Environmental Health Sciences (NIEHS), National Institutes of Health (NIH), Department of Health and Human Services (DHHS)  North Carolina USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2026,5,28]]},"reference":[{"key":"e_1_2_10_2_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.eclinm.2023.102155"},{"key":"e_1_2_10_3_1","doi-asserted-by":"publisher","DOI":"10.1186\/s12978\u2010025\u201002033\u2010x"},{"key":"e_1_2_10_4_1","doi-asserted-by":"publisher","DOI":"10.1111\/j.1365\u20103016.2008.00965.x"},{"key":"e_1_2_10_5_1","doi-asserted-by":"publisher","DOI":"10.1111\/ppe.13029"},{"key":"e_1_2_10_6_1","doi-asserted-by":"publisher","DOI":"10.1186\/s13293\u2010016\u20100119\u20101"},{"key":"e_1_2_10_7_1","doi-asserted-by":"publisher","DOI":"10.1080\/08897077.2013.804483"},{"key":"e_1_2_10_8_1","doi-asserted-by":"publisher","DOI":"10.1111\/j.1471\u20100528.2004.00311.x"},{"key":"e_1_2_10_9_1","doi-asserted-by":"publisher","DOI":"10.1001\/jamapediatrics.2017.3785"},{"key":"e_1_2_10_10_1","doi-asserted-by":"publisher","DOI":"10.1093\/humrep\/den389"},{"key":"e_1_2_10_11_1","doi-asserted-by":"publisher","DOI":"10.1111\/j.1471\u20100528.1984.tb04830.x"},{"key":"e_1_2_10_12_1","doi-asserted-by":"publisher","DOI":"10.1038\/s41746\u2010019\u20100152\u20107"},{"issue":"2","key":"e_1_2_10_13_1","doi-asserted-by":"crossref","first-page":"397","DOI":"10.2307\/2530453","article-title":"Basal Body Temperature, Ovulation and the Risk of Conception, With Special Reference to the Lifetimes of Sperm and Egg","volume":"38","author":"Royston J. 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