{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,12]],"date-time":"2026-01-12T14:50:32Z","timestamp":1768229432484,"version":"3.49.0"},"reference-count":51,"publisher":"Wiley","issue":"6","license":[{"start":{"date-parts":[[2025,10,22]],"date-time":"2025-10-22T00:00:00Z","timestamp":1761091200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Pregnancy"],"published-print":{"date-parts":[[2025,11]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:sec>\n                    <jats:title>Introduction<\/jats:title>\n                    <jats:p>Severe acute respiratory syndrome coronavirus 2 (SARS\u2010CoV\u20102) infection during pregnancy is associated with an increased risk of preterm birth (PTB). The aim of the study was to investigate the effect of timing of SARS\u2010CoV\u20102 infection during pregnancy on PTB risk and whether the risk is related to the interval from infection onset. We also studied whether the association is driven primarily by spontaneous or iatrogenic PTB, as well as to what extent disease severity, viral variant, background characteristics, and vaccination status affect the risk for PTB.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Material and methods<\/jats:title>\n                    <jats:p>\n                      This is a Swedish population\u2013based register study including all singleton pregnancies registered in the Swedish Pregnancy Register with estimated date of birth between March 1, 2020 and May 31, 2022 (\n                      <jats:italic>n<\/jats:italic>\n                      \u00a0=\u00a0233,335). Data on SARS\u2010CoV\u20102 test positivity, vaccination status, and disease severity were retrieved from mandatory Swedish health registers. Cox regression analyses with time\u2010varying covariates were performed to investigate the association of testing positive for SARS\u2010CoV\u20102 during pregnancy and risk of PTB.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      There was a significant (\n                      <jats:italic>p<\/jats:italic>\n                      \u00a0=\u00a00.047) interaction between gestational age at the debut of SARS\u2010CoV\u20102 infection and hazard ratio (HR) for PTB within 2 weeks. The adjusted HRs (aHRs and 95% confidence interval [CI]) for PTB within 2\u00a0weeks of a positive SARS\u2010CoV\u20102 test were 6.0 (3.9\u20139.2), 6.1 (4.4\u20138.4), and 3.2 (2.7\u20133.7) for women with a positive test at 22\u201327, 28\u201331, or 32\u201336 gestational weeks, respectively. Two weeks or more after the start of a SARS\u2010CoV\u20102 infection, only a slightly increased hazard for PTB could be observed (aHR, 1.2; 95% CI, 1.0\u20131.4,\n                      <jats:italic>p<\/jats:italic>\n                      \u00a0=\u00a00.016). Excluding women admitted for SARS\u2010CoV\u20102 infection, the aHR for PTB within 2 weeks was aHR\u00a0=\u00a02.8 (95% CI, 2.4\u20133.3). The aHR for preterm birth among vaccinated infected women compared to non\u2010infected was 1.6 (95% CI, 1.2\u20132.2). The corresponding aHR for women who had a SARS\u2010CoV\u20102 infection without a previous vaccination was 3.2 (95% CI, 2.3\u20134.3). Thus, vaccinated infected women had a significantly lower risk for PTB than had women without vaccination before infection (\n                      <jats:italic>p<\/jats:italic>\n                      for homogeneity\u00a0=\u00a00.007). The viral variants Alpha and Delta were associated with a greater risk of PTB compared with Omicron, but the risk increase was found during the entire study period.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>Pregnant women are at particularly high risk of PTB within 14 days after a SARS\u2010CoV\u20102 infection, and should be counselled on PTB symptoms to ensure that they seek medical care without delay. The increased PTB risk is partly mitigated by vaccination against SARS\u2010CoV\u20102.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1002\/pmf2.70136","type":"journal-article","created":{"date-parts":[[2025,10,22]],"date-time":"2025-10-22T16:00:17Z","timestamp":1761148817000},"source":"Crossref","is-referenced-by-count":0,"title":["Severe acute respiratory syndrome coronavirus 2 and preterm birth, clinical implications\u2014A register\u2010based cohort study from Sweden"],"prefix":"10.1002","volume":"1","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-0008-6946","authenticated-orcid":false,"given":"Lisa","family":"Berglin","sequence":"first","affiliation":[{"name":"Department of Obstetrics and Gynaecology Institute of Clinical Sciences Sahlgrenska Academy University of Gothenburg  Gothenburg Sweden"},{"name":"Region V\u00e4stra G\u00f6taland Department of Obstetrics and Gynaecology Sahlgrenska University Hospital  Gothenburg Sweden"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Karin","family":"K\u00e4ll\u00e9n","sequence":"additional","affiliation":[{"name":"Department of Clinical Sciences Faculty of Medicine Lund University  Lund Sweden"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5079-2374","authenticated-orcid":false,"given":"Bo","family":"Jacobsson","sequence":"additional","affiliation":[{"name":"Department of Obstetrics and Gynaecology Institute of Clinical Sciences Sahlgrenska Academy University of Gothenburg  Gothenburg Sweden"},{"name":"Region V\u00e4stra G\u00f6taland Department of Obstetrics and Gynaecology Sahlgrenska University Hospital  Gothenburg Sweden"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Verena","family":"Sengpiel","sequence":"additional","affiliation":[{"name":"Department of Obstetrics and Gynaecology Institute of Clinical Sciences Sahlgrenska Academy University of Gothenburg  Gothenburg Sweden"},{"name":"Region V\u00e4stra G\u00f6taland Department of Obstetrics and Gynaecology Sahlgrenska University Hospital  Gothenburg Sweden"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"311","published-online":{"date-parts":[[2025,10,22]]},"reference":[{"key":"e_1_2_11_2_1","doi-asserted-by":"publisher","DOI":"10.1136\/bmj.m3320"},{"key":"e_1_2_11_3_1","doi-asserted-by":"publisher","DOI":"10.1016\/S2589-7500(21)00250-8"},{"key":"e_1_2_11_4_1","doi-asserted-by":"publisher","DOI":"10.1542\/peds.2022-059595"},{"key":"e_1_2_11_5_1","doi-asserted-by":"publisher","DOI":"10.1038\/s41372-022-01467-6"},{"key":"e_1_2_11_6_1","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pone.0270893"},{"key":"e_1_2_11_7_1","doi-asserted-by":"publisher","DOI":"10.1111\/aogs.14160"},{"key":"e_1_2_11_8_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.ajog.2022.11.1301"},{"key":"e_1_2_11_9_1","doi-asserted-by":"publisher","DOI":"10.1093\/infdis\/jiab626"},{"key":"e_1_2_11_10_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.lana.2021.100027"},{"key":"e_1_2_11_11_1","doi-asserted-by":"publisher","DOI":"10.1016\/S2213-2600(22)00360-5"},{"key":"e_1_2_11_12_1","doi-asserted-by":"publisher","DOI":"10.1111\/ppe.12944"},{"key":"e_1_2_11_13_1","doi-asserted-by":"publisher","DOI":"10.1186\/s12884-022-05101-3"},{"issue":"9","key":"e_1_2_11_14_1","first-page":"704","article-title":"Does Asymptomatic\/Uncomplicated SARS\u2010CoV\u20102 Infection During Pregnancy Increase the Risk of Spontaneous Preterm Birth?","volume":"94","author":"Kumru P.","year":"2022","journal-title":"Ginekologia Polska"},{"issue":"116","key":"e_1_2_11_15_1","first-page":"FR6F","article-title":"F\u00f6rtidsb\u00f6rd St\u00f6rsta Perinatala Problemet","volume":"2019","author":"Jacobsson B.","year":"2019","journal-title":"L\u00e4kartidningen"},{"key":"e_1_2_11_16_1","doi-asserted-by":"publisher","DOI":"10.1177\/03000605231203843"},{"key":"e_1_2_11_17_1","doi-asserted-by":"publisher","DOI":"10.1111\/aogs.13266"},{"key":"e_1_2_11_18_1","unstructured":"The Public Health Agency of Sweden.2021.The Swedish Register for Mandatory Registration of Notifiable Infectious Disease (SmiNet).Stockholm:The Public Health Agency of Sweden. 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