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Because cotinine has a shorter half-life in pregnant than non-pregnant women and analytical methods differ, population-specific cut-offs are needed. Spot urine samples were collected from term pregnant women who self-reported as non-smokers or smokers and cotinine was measured by gas chromatography-mass spectrometry to validate smoking status.",{"@graph":69,"@context":122},[70,84,105],{"@type":71,"itemListElement":72},"BreadcrumbList",[73,77,79,82],{"item":74,"name":75,"@type":76,"position":8},"https://docshare.wps.com","Home","ListItem",{"item":78,"name":9,"@type":76,"position":14},"https://docshare.wps.com/document/",{"item":80,"name":40,"@type":76,"position":81},"https://docshare.wps.com/document/research-report/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/urinary-cotinine-cut-off-value-in-categorising-cigarette-smoking-status-in-healthy-pregnant-women-at-term/444670/",{"url":83,"name":65,"@type":85,"image":86,"author":91,"headline":65,"publisher":94,"fileFormat":97,"inLanguage":63,"description":67,"dateModified":98,"datePublished":99,"encodingFormat":97,"isAccessibleForFree":100,"interactionStatistic":101},"DigitalDocument",{"url":87,"@type":88,"width":89,"height":90},"https://docshare.wps.com/thumbnails/urinary-cotinine-cut-off-value-in-categorising-cigarette-smoking-status-in-healthy-pregnant-women-at-term/444670.png","ImageObject",300,407,{"name":92,"@type":93},"Ben ","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-10-04","2026-09-29",true,{"@type":102,"interactionType":103,"userInteractionCount":81},"InteractionCounter",{"@type":104},"ViewAction",{"@type":106,"mainEntity":107},"FAQPage",[108,114,118],{"name":109,"@type":110,"acceptedAnswer":111},"Why is urinary cotinine used in pregnancy smoking studies?","Question",{"text":112,"@type":113},"Urinary cotinine, a nicotine metabolite, helps address underreporting of tobacco smoke exposure and provides an objective biomarker for smoking status.","Answer",{"name":115,"@type":110,"acceptedAnswer":116},"What limitation requires using pregnancy-specific cotinine cut-offs?",{"text":117,"@type":113},"Cotinine’s half-life is shorter in pregnant women, and different analytical techniques can yield different cotinine levels, so general-population thresholds may misclassify status.",{"name":119,"@type":110,"acceptedAnswer":120},"What cut-off values best distinguish term pregnant non-smokers from smokers?",{"text":121,"@type":113},"ROC analysis indicated optimal cut-offs of 120 µg/L or 144 µg/g creatinine, with about 94% sensitivity and 96%–97% specificity.","https://schema.org",{"og:url":83,"og:type":124,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":126,"canonical":83},"index,follow",{"doc_id":128,"site_id":62},444670,1790741576,{"code":4,"msg":5,"data":131},{"doc_id":128,"user_id":132,"nickname":92,"user_avatar":133,"doc_module":4,"category_id":39,"category_name":40,"doc_title":65,"doc_description":67,"doc_content":134,"file_id":135,"file_url":136,"file_type":137,"file_size":138,"view_count":81,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":39,"language":139,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":140,"faqs":141,"seo_title":142,"seo_description":67,"update_tm":143,"read_time":46},2336478951081,"https://ap-avatar.wpscdn.com/davatar_276721f389ce27ea32af1340a28f341c","251  \nBrajenović N, et al. Urinary cotinine cut-off value in categorising cigarette smoking status in healthy pregnant women at term Arh Hig Rada Toksikol 2025;76:251–258  \nOriginal article  \nDOI: 10.2478/aiht-2025-76-4052  \nUrinary cotinine cut-off value in categorising cigarette smoking status in healthy pregnant women at term  \nNataša Brajenović1, Irena Brčić Karačonji1,2, Andreja Jurič1, Jelena Kovačić1, Sandra Stasenko3, Tatjana Mioč3,4, Iva Miškulin5, Lana Škrgatić5, Martina Piasek1, and Jasna Jurasović1  \n1 Institute for Medical Research and Occupational Health, Zagreb, Croatia  \n2 University of Rijeka Faculty of Health Studies, Croatia  \n3 Merkur University Hospital, Zagreb, Croatia  \n4 Poliklinika Harni, Zagreb, Croatia  \n5 University Hospital Centre Zagreb, Zagreb, Croatia  \n[Received in October 2025; Similarity Check in October 2025; Accepted in December 2025]  \nFuture mothers tend to underreport intentional or unintentional tobacco smoke exposure to avoid social stigma, and urine levels of cotinine, the major metabolite of nicotine can serve as a valuable biomarker of tobacco smoke exposure to resolve such uncertainties. When establishing the cut-off level to discern non-smokers from active smokers, however, one should bear in mind the shorter half-life of cotinine in pregnant than non-pregnant women to avoid misclassification of maternal smoking status. The aim of our study was to determine the urinary cotinine cut-off level to objectively detect active smokers and to see if any participant characteristics were associated with underreporting. To do that, we collected spot urine samples from pregnant women with normal vaginal delivery at term, self-reported as non-smokers (n=123) or smokers (n=33), in the maternity ward before delivery. We also took their sociodemographic, cigarette smoking, and clinical data, as well as clinical data on their newborns using a questionnaire. To ensure objective classification of participants by smoking status, cotinine levels were quantified in urine using gas chromatography-mass spectrometry. The receiver operating characteristic (ROC) curve analysis showed that the optimal cut-off value of urinary cotinine to discern pregnant non-smokers from smokers at term were 120 µg/L or 144 µg/g creatinine, yielding 94 % sensitivity and 96 % or 97 % specificity. Respective to these cut-off values, 4.1 % and 3.3 % of self-reported non-smokers were classified as current smokers. Our findings support the use of urinary cotinine, whenever feasible, to reduce reporting bias in pregnancy studies, and, given the altered nicotine metabolism during pregnancy, future epidemiological studies should bear in mind that urinary cotinine cut-off values may depend on the stage of pregnancy.  \nKEY WORDS: biomonitoring; creatinine-adjusted cotinine; pregnancy; second-hand smoke; smoking validation  \nHealth risks associated with cigarette smoking in women include a myriad of disorders, ranging from effects on maternal reproductive health and postpartum disorders to chronic diseases and malignancies. In pregnancy, smoking is linked to placental and foetal membrane disorders as well as health risks in the offspring that can be manifested as a number of conditions soon after birth and/or later in adult life (1–7). According to a meta-analysis by Lange et al.  \n(8), the estimated prevalence of smoking during pregnancy in Europe was 8.1 %, with 30.6 % of daily smokers continuing to smoke throughout pregnancy. In Croatia, this prevalence exceeds the European average with some of the highest reported rates before and during pregnancy (9) . A recent Eurostat report for 2019 confirmed Croatia as one of the EU countries with the highest smoking prevalence among women aged >15 years and ranking second among women aged 15–29, of whom 26.6 % reported smoking daily or occasionally. Back then, fewer than 1 % women used smokeless tobacco products (10) .  \nCorresponding author: Irena Brčić Karačonji, Institute for Medical Resea","cbCaitye6jJXxlEw","https://ap.wps.com/l/cbCaitye6jJXxlEw","pdf",764133,"English","# Aim and rationale\n## Study design and sample collection\n## Biomarker measurement and ROC analysis\n## Key cut-off values and implications","[{\"question\":\"Why is urinary cotinine used in pregnancy smoking studies?\",\"answer\":\"Urinary cotinine, a nicotine metabolite, helps address underreporting of tobacco smoke exposure and provides an objective biomarker for smoking status.\"},{\"question\":\"What limitation requires using pregnancy-specific cotinine cut-offs?\",\"answer\":\"Cotinine’s half-life is shorter in pregnant women, and different analytical techniques can yield different cotinine levels, so general-population thresholds may misclassify status.\"},{\"question\":\"What cut-off values best distinguish term pregnant non-smokers from smokers?\",\"answer\":\"ROC analysis indicated optimal cut-offs of 120 µg/L or 144 µg/g creatinine, with about 94% sensitivity and 96%–97% specificity.\"}]","Urinary cotinine cut-off value in categorising cigarette smoking status in healthy pregnant women at term | PDF",1790708843]