{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,2]],"date-time":"2026-06-02T00:15:00Z","timestamp":1780359300016,"version":"3.54.1"},"update-to":[{"DOI":"10.1371\/journal.pmed.1004747","type":"new_version","label":"New version","source":"publisher","updated":{"date-parts":[[2026,5,27]],"date-time":"2026-05-27T00:00:00Z","timestamp":1779840000000}}],"reference-count":51,"publisher":"Public Library of Science (PLoS)","issue":"5","license":[{"start":{"date-parts":[[2026,5,20]],"date-time":"2026-05-20T00:00:00Z","timestamp":1779235200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"NIH","award":["DK123330"],"award-info":[{"award-number":["DK123330"]}]},{"name":"NIH","award":["R01HD104756"],"award-info":[{"award-number":["R01HD104756"]}]},{"name":"Gates Foundation","award":["090035"],"award-info":[{"award-number":["090035"]}]},{"name":"NIH\/ NHLBI","award":["K08 HL146963"],"award-info":[{"award-number":["K08 HL146963"]}]},{"DOI":"10.13039\/100009633","name":"NIH\/NICHD","doi-asserted-by":"crossref","award":["5K12HD103096\u201304"],"award-info":[{"award-number":["5K12HD103096\u201304"]}],"id":[{"id":"10.13039\/100009633","id-type":"DOI","asserted-by":"crossref"}]},{"name":"NIH\/ NIDDK","award":["K26DK138346"],"award-info":[{"award-number":["K26DK138346"]}]},{"name":"NIH","award":["T32DK007028\u201347S1"],"award-info":[{"award-number":["T32DK007028\u201347S1"]}]},{"DOI":"10.13039\/100016392","name":"Center for Global Health, Massachusetts General Hospital","doi-asserted-by":"publisher","award":["MGH Claflin Distinguished Scholar Award"],"award-info":[{"award-number":["MGH Claflin Distinguished Scholar Award"]}],"id":[{"id":"10.13039\/100016392","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100016392","name":"Center for Global Health, Massachusetts General Hospital","doi-asserted-by":"publisher","award":["MGH Physician-Scientist Development Award"],"award-info":[{"award-number":["MGH Physician-Scientist Development Award"]}],"id":[{"id":"10.13039\/100016392","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["www.plosmedicine.org"],"crossmark-restriction":false},"short-container-title":["PLoS Med"],"abstract":"<jats:sec id=\"sec001\">\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>Pregnancy alters hematologic state as measured by complete blood count (CBC), but the longitudinal changes in CBC indices that define healthy pregnancies are not well established. In a large cohort based at an academic health system in the United States, we aimed to define reference intervals and typical longitudinal changes in CBC indices during pregnancy. We then tested for associations between extreme CBC values for gestational age or extreme longitudinal changes in CBC indices and obstetric complications.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec002\">\n                    <jats:title>Methods and findings<\/jats:title>\n                    <jats:p>\n                      We studied nine CBC indices in individuals with singleton pregnancies who delivered after 30 weeks\u2019 gestation and presented for prenatal care prior to 20 weeks. The electronic health record (EHR)-based Maternal Health Cohort (Massachusetts General Hospital; 1998\u20132016) formed our discovery cohort of 45,992 pregnancies, 18% of which had relevant complications. We developed a validation cohort of 48,868, 27% with complications from EHR data in the Mass General Brigham healthcare system from 2016 to 2024. In pregnancies without complications in the discovery cohort, we derived gestational-age-specific reference intervals (2.5th\u201397.5th percentile) and established typical intra-pregnancy longitudinal changes. In the validation cohort, we then tested CBC values outside of the 26\u201329 weeks\u2019 gestation reference interval and CBC rare changes (uncommon changes in magnitude and direction) between 7\u201314 and 26\u201329 weeks\u2019 gestation for association with a composite outcome (hypertensive disorders of pregnancy, small for gestational age birthweight, preterm birth) and its individual components using generalized estimating equations. Derived reference intervals differed from those in the literature for mean red cell volume, mean red cell hemoglobin, red cell count, and mean red cell hemoglobin concentration; reference intervals for other indices were similar to those previously published. In validation, hematocrit, hemoglobin, and red cell count values above their gestational-age specific reference intervals were associated with increased risk of the composite obstetric outcome: odds ratios (ORs) of 1.4 (95% CI [1.2, 1.5]\n                      <jats:italic>p<\/jats:italic>\n                      \u2009&lt;\u20090.0001) for hematocrit; 1.6 (95% CI [1.4, 1.8]\n                      <jats:italic>p<\/jats:italic>\n                      \u2009&lt;\u20090.0001) for hemoglobin; and 1.6 (95% CI [1.4, 1.7]\n                      <jats:italic>p<\/jats:italic>\n                      \u2009&lt;\u20090.0001) for red cell count. Uncommon increases in hemoglobin (&gt;0.67\u2009g\/dL) or red cell count (&gt;0.07 10\n                      <jats:sup>6<\/jats:sup>\n                      \/mm\n                      <jats:sup>3<\/jats:sup>\n                      ) between 7\u201314 weeks\u2019 and 26\u201329 weeks\u2019 gestation were associated with increased risk for preterm birth, OR for hemoglobin 1.9 (95% CI [1.5, 2.5]\n                      <jats:italic>p<\/jats:italic>\n                      \u2009&lt;\u20090.0001) and red cell count 2.1 (95% CI [1.7, 2.6]\n                      <jats:italic>p<\/jats:italic>\n                      \u2009&lt;\u20090.0001). Limitations include the retrospective nature of the study and the exclusion of pregnancies without prenatal care prior to 20 weeks\u2019 and pregnancies delivered before 29 weeks\u2019 gestation.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec003\">\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>Elevated red blood cell-related measurements and unusually large intra-pregnancy increases in those measures are associated with subsequent obstetric complications.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1371\/journal.pmed.1004747","type":"journal-article","created":{"date-parts":[[2026,5,20]],"date-time":"2026-05-20T17:52:21Z","timestamp":1779299541000},"page":"e1004747","update-policy":"https:\/\/doi.org\/10.1371\/journal.pmed.corrections_policy","source":"Crossref","is-referenced-by-count":0,"title":["Associations between hematologic dynamics during pregnancy and obstetric 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Beguin","year":"1991","journal-title":"Blood"},{"issue":"11","key":"pmed.1004747.ref014","doi-asserted-by":"crossref","first-page":"611","DOI":"10.1007\/s00277-002-0549-1","article-title":"Tissue plasminogen activator levels change with plasma fibrinogen concentrations during pregnancy","volume":"81","author":"JW Choi","year":"2002","journal-title":"Ann Hematol"},{"issue":"11","key":"pmed.1004747.ref015","doi-asserted-by":"crossref","first-page":"1052","DOI":"10.1002\/pd.2126","article-title":"Longitudinal study of platelet size changes in gestation and predictive power of elevated MPV in development of pre-eclampsia","volume":"28","author":"O Dundar","year":"2008","journal-title":"Prenat Diagn"},{"issue":"4","key":"pmed.1004747.ref016","first-page":"86","article-title":"Platelets and leucocyte counts in pregnancy","volume":"42","author":"SA Karim","year":"1992","journal-title":"J Pak Med 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Scand"},{"key":"pmed.1004747.ref020","doi-asserted-by":"crossref","first-page":"281","DOI":"10.1016\/j.cll.2013.03.016","article-title":"Anemia in pregnancy \u2013 ClinicalKey","volume":"33","author":"K Horowitz","year":"2013","journal-title":"Clin Lab Med"},{"issue":"2","key":"pmed.1004747.ref021","doi-asserted-by":"crossref","first-page":"159","DOI":"10.1016\/S0925-5710(97)00031-5","article-title":"Serum erythropoietin during normal pregnancy: relationship to hemoglobin and iron status markers and impact of iron supplementation in a longitudinal, placebo-controlled study on 118 women","volume":"66","author":"N Milman","year":"1997","journal-title":"Int J Hematol"},{"issue":"2","key":"pmed.1004747.ref022","doi-asserted-by":"crossref","first-page":"101","DOI":"10.1111\/j.1471-0528.1983.tb08891.x","article-title":"Iron requirement in normal pregnancy as assessed by serum ferritin, serum transferrin saturation and erythrocyte protoporphyrin determinations","volume":"90","author":"I Romslo","year":"1983","journal-title":"Br J Obstet Gynaecol"},{"key":"pmed.1004747.ref023","article-title":"Pregnancy and postpartum dynamics revealed by an atlas of millions of lab tests","author":"A Bar","year":"2023","journal-title":"bioRxiv"},{"issue":"2","key":"pmed.1004747.ref024","doi-asserted-by":"crossref","first-page":"100814","DOI":"10.1016\/j.ajogmf.2022.100814","article-title":"Assessment of the validity of administrative data for gestational diabetes ascertainment","volume":"5","author":"S Hsu","year":"2023","journal-title":"Am J Obstet Gynecol MFM"},{"issue":"3","key":"pmed.1004747.ref025","doi-asserted-by":"crossref","first-page":"594","DOI":"10.1097\/AOG.0000000000005278","article-title":"Gestational glucose intolerance and birth weight-related complications","volume":"142","author":"J Maya","year":"2023","journal-title":"Obstet Gynecol"},{"key":"pmed.1004747.ref026","doi-asserted-by":"crossref","first-page":"83","DOI":"10.2337\/dc22-1390","article-title":"Gestational glucose intolerance and risk of future diabetes","volume":"46","author":"DJ Selen","year":"2023","journal-title":"Diabetes Care"},{"key":"pmed.1004747.ref027","volume-title":"Biological variation: from principles to practice","author":"C Fraser","year":"2001"},{"key":"pmed.1004747.ref028","unstructured":"Cunningham FG. Normal reference ranges for laboratory values in pregnancy \u2013 UpToDate. In: UpToDate [Internet]. Jan 2023 [cited 9 Feb 2023]. Available from: https:\/\/www-uptodate-com.treadwell.idm.oclc.org\/contents\/normal-reference-ranges-for-laboratory-values-in-pregnancy?search=reference%20ranges%20in%20pregnancy&source=search_result&selectedTitle=1~150&usage_type=default&display_rank=1"},{"key":"pmed.1004747.ref029","unstructured":"Normal reference ranges and laboratory values in pregnancy. In: perinatology.com [Internet]. 22 Dec 2023 [cited 22 Dec 2023]. Available from: https:\/\/www.perinatology.com\/Reference\/Reference%20Ranges\/Reference%20for%20Serum.htm"},{"key":"pmed.1004747.ref030","article-title":"Anemia in pregnancy: ACOG practice bulletin, number 233","volume":"138","year":"2021","journal-title":"Obstet Gynecol"},{"key":"pmed.1004747.ref031","unstructured":"Aarsand A, Fernandez-Calle P, Webster C, Coskun A, Gonzales-Lao E, Diaz-Garzon J, et al. The EFLM biological variation database. [cited 26 Jan 2023]. 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Freaney","year":"2022","journal-title":"J Am Heart Assoc"},{"issue":"3","key":"pmed.1004747.ref039","doi-asserted-by":"crossref","first-page":"216","DOI":"10.1111\/j.1471-0528.1993.tb15233.x","article-title":"Retrospective analysis of platelet numbers and volumes in normal pregnancy and in pre-eclampsia","volume":"100","author":"Y Ahmed","year":"1993","journal-title":"Br J Obstet Gynaecol"},{"key":"pmed.1004747.ref040","doi-asserted-by":"crossref","first-page":"205","DOI":"10.11604\/pamj.2018.29.205.13043","article-title":"Hematological parameters of the blood count in a healthy population of pregnant women in the Northwest of Morocco (Tetouan-M\u2019diq-Fnideq provinces)","volume":"29","author":"S Bakrim","year":"2018","journal-title":"Pan Afr Med J"},{"issue":"6","key":"pmed.1004747.ref041","article-title":"Establishment of reference intervals for complete blood count parameters during normal pregnancy in Beijing","volume":"31","author":"A Li","year":"2017","journal-title":"J Clin 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