{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,14]],"date-time":"2026-04-14T15:57:18Z","timestamp":1776182238574,"version":"3.50.1"},"reference-count":66,"publisher":"Wiley","issue":"23","license":[{"start":{"date-parts":[[2023,10,31]],"date-time":"2023-10-31T00:00:00Z","timestamp":1698710400000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":["physoc.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["The Journal of Physiology"],"published-print":{"date-parts":[[2023,12]]},"abstract":"<jats:sec><jats:title>Abstract<\/jats:title><jats:p>Late gestational supine positioning reduces maternal cardiac output due to inferior vena caval (IVC) compression, despite increased collateral venous return. However, little is known about the impact of maternal position on oxygen (O<jats:sub>2<\/jats:sub>) delivery and consumption of the gravid uterus, fetus, placenta and lower limbs. We studied the effects of maternal positioning on these parameters in 20 healthy pregnant subjects at 36\u00a0\u00b1\u00a02\u00a0weeks using magnetic resonance imaging (MRI); a follow\u2010up MRI was performed 6\u2010months postpartum (<jats:italic>n<\/jats:italic>\u00a0=\u00a016\/20). MRI techniques included phase\u2010contrast and T1\/T2 relaxometry for blood flow and oximetry imaging, respectively. O<jats:sub>2<\/jats:sub> transport was measured in the following vessels (bilateral where appropriate): maternal abdominal descending aorta (DAo<jats:sub>abdo<\/jats:sub>), IVC, ovarian, paraspinal veins (PSV), uterine artery (UtA) and external iliacs, and umbilical. Maternal cardiac output was measured by summing DAo<jats:sub>thoracic<\/jats:sub> and superior vena cava flows. Supine mothers (<jats:italic>n<\/jats:italic>\u00a0=\u00a06) had lower cardiac output and O<jats:sub>2<\/jats:sub> delivery in the DAo<jats:sub>abdo<\/jats:sub>, UtA and external iliac arteries, and higher PSV flow than those in either the left (<jats:italic>n<\/jats:italic>\u00a0=\u00a08) or right (<jats:italic>n<\/jats:italic>\u00a0=\u00a06) lateral positions during MRI. However, O<jats:sub>2<\/jats:sub> consumption in the gravid uterus, fetus, placenta and lower limbs was unaffected by maternal positioning. The ratio of IVC\/PSV flow decreased in supine mothers while ovarian venous flow and O<jats:sub>2<\/jats:sub> saturation were unaltered, suggesting a major route of pelvic venous return unaffected by maternal position. Placental\u2013fetal O<jats:sub>2<\/jats:sub> transport and consumption were similar between left and right lateral maternal positions. In comparison to non\u2010pregnant findings, DAo<jats:sub>abdo<\/jats:sub> and UtA O<jats:sub>2<\/jats:sub> delivery and pelvic O<jats:sub>2<\/jats:sub> consumption increased, while lower\u2010limb consumption remained constant , despite reduced external iliac artery O<jats:sub>2<\/jats:sub> delivery in late gestation.\n<jats:boxed-text content-type=\"graphic\" position=\"anchor\"><jats:graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" mimetype=\"image\/png\" position=\"anchor\" specific-use=\"enlarged-web-image\" xlink:href=\"graphic\/tjp15795-gra-0001-m.png\"><jats:alt-text>image<\/jats:alt-text><\/jats:graphic><\/jats:boxed-text><\/jats:p><\/jats:sec><jats:sec><jats:title>Key points<\/jats:title><jats:p><jats:list list-type=\"bullet\">\n<jats:list-item><jats:p>Though sleeping supine during the third trimester is associated with an increased risk of antepartum stillbirth, the underlying biological mechanisms are not fully understood.<\/jats:p><\/jats:list-item>\n<jats:list-item><jats:p>Maternal cardiac output and uteroplacental flow are reduced in supine mothers due to inferior vena caval compression from the weight of the gravid uterus.<\/jats:p><\/jats:list-item>\n<jats:list-item><jats:p>This MRI study provides a comprehensive circulatory assessment, demonstrating reduced maternal cardiac output and O<jats:sub>2<\/jats:sub> delivery (uteroplacental, lower body) in supine compared to lateral positioning; however, O<jats:sub>2<\/jats:sub> consumption (gravid uterus, fetus, placenta, lower limbs) was preserved.<\/jats:p><\/jats:list-item>\n<jats:list-item><jats:p>Unlike other mammalian species, the ovarian veins conduct substantial venous return from the human pregnant uterus that is unaffected by maternal positioning. Lumbar paraspinal venous flow increased in supine mothers. These observations may have important considerations during major pelvic surgery in pregnancy (i.e. placenta percreta).<\/jats:p><\/jats:list-item>\n<jats:list-item><jats:p>Future studies should address the importance of maternal positioning as a potential tool to deliver improved perinatal outcomes in pregnancies with compromised uteroplacental O<jats:sub>2<\/jats:sub> delivery.<\/jats:p><\/jats:list-item>\n<\/jats:list><\/jats:p><\/jats:sec>","DOI":"10.1113\/jp285097","type":"journal-article","created":{"date-parts":[[2023,10,31]],"date-time":"2023-10-31T14:53:20Z","timestamp":1698764000000},"page":"5413-5436","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":7,"title":["Feasibility of MRI assessment of maternal\u2013fetal oxygen transport and consumption relative to maternal position in healthy late gestational pregnancies"],"prefix":"10.1113","volume":"601","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-3272-3812","authenticated-orcid":false,"given":"Brahmdeep S.","family":"Saini","sequence":"first","affiliation":[{"name":"Heart Centre, Division of Cardiology The Hospital for Sick Children  Toronto Ontario Canada"},{"name":"Translational Medicine, Peter Gilgan Centre for Research and Learning The Hospital for Sick Children  Toronto Ontario Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Robin","family":"Ducas","sequence":"additional","affiliation":[{"name":"Department of Internal Medicine, Section of Cardiology, Max Rady College of Medicine, Rady Faculty of Health Sciences University of Manitoba  Winnipeg Manitoba Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jack R.T.","family":"Darby","sequence":"additional","affiliation":[{"name":"Early Origins of Adult Health Research Group, Health and Biomedical Innovation, UniSA: Clinical and Health 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