{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,9]],"date-time":"2026-09-09T01:22:07Z","timestamp":1788916927297,"version":"build-2803163510"},"reference-count":15,"publisher":"Institute of Physiology of the Czech Academy of Sciences","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Physiol Res"],"published-print":{"date-parts":[[2024,11,29]]},"abstract":"<jats:p>The fetus develops normally in a hypoxic environment but exaggerated hypoxia late in pregnancy is a worrisome sign often observed in hypertensive disorders of pregnancy, placental insufficiency, or fetal growth restriction (FGR). Serial fetal biometry and the cerebroplacental ratio (CPR, calculated as the middle cerebral artery [MCA] \/ the umbilical artery [UmbA] pulsatility indices [PI]), are commonly used to indicate fetal \u201cbrain sparing\u201d resulting from exaggerated fetal hypoxia. But unclear is the extent to which a low CPR indicates pathology or is a physiological response for maintaining cerebral blood flow. We studied 31 appropriate for gestational age (AGA) pregnancies at low (LA, 1670 m) or high (HA, 2879 m) altitude, given the chronic hypoxia imposed by HA residence, and 54 LA women with a clinical diagnosis of FGR. At week 34, the MCA PI was lower in the LA-FGR than the LA-AGA group but lower still in the HA-AGA compared to either LA groups due to a trend toward higher end-diastolic velocity (EDV). We concluded that the lower MCA PI was likely due to greater cerebral vasodilation in the HA AGA group and an indication of physiological versus pathological fetal hypoxia. Future reporting of serial MCA and UmbA values and their determinants along with the CPR could improve our ability to distinguish between physiological and pathological fetal brain sparing.<\/jats:p>","DOI":"10.33549\/physiolres.935482","type":"journal-article","created":{"date-parts":[[2024,11,22]],"date-time":"2024-11-22T18:46:05Z","timestamp":1732301165000},"page":"S487-S493","source":"Crossref","is-referenced-by-count":4,"title":["Does Hypoxia Prompt Fetal Brain-Sparing in the Absence of Fetal Growth Restriction?"],"prefix":"10.33549","author":[{"given":"LG","family":"Moore","sequence":"first","affiliation":[{"name":"Department of Obstetrics and Gynecology, University of Colorado Denver \u2013 Anschutz Medical Campus, Aurora, Colorado, USA. Lorna.Moore@cuanschutz.edu"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"CG","family":"Julian","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"RA","family":"Lorca","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"DC","family":"Ragan","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"D","family":"Gumina","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"JC","family":"Hobbins","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"19169","published-online":{"date-parts":[[2024,11,22]]},"reference":[{"key":"ref0","doi-asserted-by":"publisher","unstructured":"Jauniaux E, Gulbis B, and G.J. Burton, Physiological implications of the materno-fetal oxygen gradient in human early pregnancy. Reprod Biomed Online 2003;7:250-253. https:\/\/doi.org\/10.1016\/S1472-6483(10)61760-9","DOI":"10.1016\/s1472-6483(10)61760-9"},{"key":"ref1","doi-asserted-by":"publisher","unstructured":"Burton GJ. Oxygen, the Janus gas; its effects on human placental development and function. J Anat 2009;215:27-35. https:\/\/doi.org\/10.1111\/j.1469-7580.2008.00978.x","DOI":"10.1111\/j.1469-7580.2008.00978.x"},{"key":"ref2","doi-asserted-by":"crossref","unstructured":"Lees CC, Romero R, Stampalija T, Dall'Asta A, DeVore GA, Prefumo F, Frusca T, et al. Clinical Opinion: The diagnosis and management of suspected fetal growth restriction: an evidence-based approach. Am J Obstet Gynecol 2022;226:366-378. https:\/\/doi.org\/10.1016\/j.ajog.2021.11.1357","DOI":"10.1016\/j.ajog.2021.11.1357"},{"key":"ref3","doi-asserted-by":"publisher","unstructured":"Giussani DA. The fetal brain sparing response to hypoxia: physiological mechanisms. J Physiol 2016;594:1215-1230. https:\/\/doi.org\/10.1113\/JP271099","DOI":"10.1113\/jp271099"},{"key":"ref4","doi-asserted-by":"publisher","unstructured":"Jensen GM, Moore LG. The effect of high altitude and other risk factors on birthweight: independent or interactive effects? Am J Public Health 1997;87:1003-1007. https:\/\/doi.org\/10.2105\/AJPH.87.6.1003","DOI":"10.2105\/ajph.87.6.1003"},{"key":"ref5","unstructured":"Palmer SK, Zamudio S, Coffin C, Parker S, Stamm E, Moore LG. Quantitative estimation of human uterine artery blood flow and pelvic blood flow redistribution in pregnancy. Obstet Gynecol 1992;80:1000-1006."},{"key":"ref6","doi-asserted-by":"publisher","unstructured":"Chassen SS, Zemski-Berry K, Raymond-Whish S, Driver C, Hobbins JC, Powell TL. Altered cord blood lipid concentrations correlate with birth weight and doppler velocimetry of fetal vessels in human fetal growth restriction pregnancies. 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Best Pract Res Clin Obstet Gynaecol 2017;38:38-47. https:\/\/doi.org\/10.1016\/j.bpobgyn.2016.09.003","DOI":"10.1016\/j.bpobgyn.2016.09.003"},{"key":"ref10","doi-asserted-by":"publisher","unstructured":"Moore LG, Young D, McCullough RE, Droma T, Zamudio S. Tibetan protection from intrauterine growth restriction (IUGR) and reproductive loss at high altitude. Am J Hum Biol 2001;13:635-644. https:\/\/doi.org\/10.1002\/ajhb.1102","DOI":"10.1002\/ajhb.1102"},{"key":"ref11","doi-asserted-by":"publisher","unstructured":"Julian CG, Vargas E, Armaza JF, Wilson MJ, Niermeyer S, Moore LG. High-altitude ancestry protects against hypoxia-associated reductions in fetal growth. Arch Dis Child Fetal Neonatal Ed 2007;92:F372-F377. https:\/\/doi.org\/10.1136\/adc.2006.109579","DOI":"10.1136\/adc.2006.109579"},{"key":"ref12","doi-asserted-by":"publisher","unstructured":"Soria R, Julian CG, Vargas E, Moore LG, Giussani DA. Graduated effects of high-altitude hypoxia and highland ancestry on birth size. Pediatr Res 2013;74:633-638. https:\/\/doi.org\/10.1038\/pr.2013.150","DOI":"10.1038\/pr.2013.150"},{"key":"ref13","doi-asserted-by":"publisher","unstructured":"Dolma P, Angchuk PT, Jain V, Dadhwal V, Kular D, Williams DJ, Montgomery HE, Hillman SL. High-altitude population neonatal and maternal phenotypes associated with birthweight protection. Pediatr Res 2022;91:137-142. https:\/\/doi.org\/10.1038\/s41390-021-01593-5","DOI":"10.1038\/s41390-021-01593-5"},{"key":"ref14","doi-asserted-by":"publisher","unstructured":"Gordijn SJ, Beune IM, Thilaganathan B, Papageorghiou A, Baschat AA, Baker PN, Silver RM, Wynia K, Ganzevoort W. Consensus definition of fetal growth restriction: a Delphi procedure. 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