{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,29]],"date-time":"2026-08-29T07:10:04Z","timestamp":1787987404188,"version":"build-2784847793"},"reference-count":59,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2026,3,24]],"date-time":"2026-03-24T00:00:00Z","timestamp":1774310400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100007686","name":"Instituto Nacional de Perinatolog\u00eda","doi-asserted-by":"publisher","award":["2017-1-37"],"award-info":[{"award-number":["2017-1-37"]}],"id":[{"id":"10.13039\/501100007686","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Nutrients"],"abstract":"<jats:p>Total body water (TBW) undergoes substantial physiological expansion during pregnancy, reflecting coordinated cardiovascular, renal, and endocrine adaptations required to support maternal metabolism, uteroplacental perfusion, and fetal growth. These changes involve not only an overall increase in body water but also shifts in the distribution of extracellular water (ECW) and intracellular water (ICW), which influence maternal body composition, the interpretation of biochemical biomarkers affected by hemodilution, and pregnancy-related clinical outcomes. Despite its physiological and clinical relevance, the regulation and assessment of body-water compartments during pregnancy remain insufficiently integrated within nutritional and clinical research. This narrative review synthesizes current knowledge on the physiological regulation of TBW and its compartments across gestation and provides a critical analysis of the methodological approaches used to assess body-water distribution in pregnant populations. We review the mechanisms underlying plasma volume expansion, interstitial fluid accumulation, and tissue hydration, and discuss their implications for fetal growth, hypertensive disorders of pregnancy, and gestational diabetes mellitus. We also examine the principles, strengths, and limitations of the main techniques used to assess TBW and body-water compartments during pregnancy. Isotope dilution using stable isotopes (2H2O and H218O) remains the reference method for TBW assessment, whereas bioelectrical impedance-based approaches, including bioelectrical impedance analysis (BIA), bioelectrical impedance spectroscopy (BIS), and bioelectrical impedance vector analysis (BIVA), offer practical alternatives for longitudinal monitoring of fluid redistribution during gestation. By integrating physiological and methodological perspectives, this review provides a framework for understanding body-water dynamics during pregnancy and for selecting appropriate approaches to assess maternal body composition and hydration.<\/jats:p>","DOI":"10.3390\/nu18071031","type":"journal-article","created":{"date-parts":[[2026,3,25]],"date-time":"2026-03-25T09:11:14Z","timestamp":1774429874000},"page":"1031","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Body Water During Pregnancy: Physiology, Clinical Significance and Assessment Methods: A Narrative Review"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-8808-6739","authenticated-orcid":false,"given":"Mar\u00eda Eugenia","family":"Flores-Quijano","sequence":"first","affiliation":[{"name":"Coordinaci\u00f3n de Nutrici\u00f3n y Bioprogramaci\u00f3n, Instituto Nacional de Perinatolog\u00eda, Mexico City 11000, Mexico"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5490-1363","authenticated-orcid":false,"given":"Reyna","family":"S\u00e1mano","sequence":"additional","affiliation":[{"name":"Coordinaci\u00f3n de Nutrici\u00f3n y Bioprogramaci\u00f3n, Instituto Nacional de Perinatolog\u00eda, Mexico City 11000, Mexico"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9960-6579","authenticated-orcid":false,"given":"Edgar","family":"Barrientos-Galeana","sequence":"additional","affiliation":[{"name":"Coordinaci\u00f3n de Nutrici\u00f3n y Bioprogramaci\u00f3n, Instituto Nacional de Perinatolog\u00eda, Mexico City 11000, Mexico"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7701-9621","authenticated-orcid":false,"given":"Hector","family":"Borboa-Olivares","sequence":"additional","affiliation":[{"name":"Coordinaci\u00f3n de Nutrici\u00f3n y Bioprogramaci\u00f3n, Instituto Nacional de Perinatolog\u00eda, Mexico City 11000, Mexico"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,3,24]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"S988","DOI":"10.1016\/j.ajog.2021.11.022","article-title":"Hemodynamic pathways of gestational hypertension and preeclampsia","volume":"226","author":"Gyselaers","year":"2022","journal-title":"Am. J. Obstet. Gynecol."},{"key":"ref_2","unstructured":"Betts, J.G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., and DeSaix, P. (2025, October 13). 26.1 Body Fluids and Fluid Compartments\u2014Anatomy and Physiology|OpenStax. Available online: https:\/\/openstax.org\/books\/anatomy-and-physiology-2e\/pages\/26-1-body-fluids-and-fluid-compartments."},{"key":"ref_3","unstructured":"International Atomic Energy Agency (2010). Introduction to Body Composition Assessment Using the Deuterium Dilution Technique with Analysis of Saliva Samples by Fourier Transform Infrared Spectrometry, International Atomic Energy Agency. Available online: https:\/\/www.iaea.org\/publications\/8369\/introduction-to-body-composition-assessment-using-the-deuterium-dilution-technique-with-analysis-of-saliva-samples-by-fourier-transform-infrared-spectrometry."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"340","DOI":"10.23876\/j.krcp.22.062","article-title":"Body water percentage from childhood to old age","volume":"42","author":"Lu","year":"2023","journal-title":"Kidney Res. Clin. Pract."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"262","DOI":"10.1007\/s12662-024-00990-2","article-title":"The female athlete\u2014Reliability of body composition analyses during the female menstrual cycle in young women without hormonal contraception","volume":"55","author":"Kiefer","year":"2025","journal-title":"Ger. J. Exerc. Sport Res."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"625","DOI":"10.70252\/GVOS2163","article-title":"The Effect of the Menstrual Cycle on Body Composition Determined by Contact-Electrode Bioelectrical Impedance Analyzers","volume":"11","author":"Cumberledge","year":"2018","journal-title":"Int. J. Exerc. Sci."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"55","DOI":"10.1007\/s11599-006-9007-0","article-title":"Changes in Total Body Water and Body Fat in Young Women in the Course of Menstrual Cycle","volume":"21","year":"2006","journal-title":"Int. J. Anthropol."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"e23951","DOI":"10.1002\/ajhb.23951","article-title":"Changes in body weight and body composition during the menstrual cycle","volume":"35","author":"Kanellakis","year":"2023","journal-title":"Am. J. Hum. Biol."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"451","DOI":"10.1016\/S0950-351X(89)80011-4","article-title":"8 Volume homeostasis and osmoregulation in human pregnancy","volume":"3","author":"Davison","year":"1989","journal-title":"Bailli\u00e8res Clin. Endocrinol. Metab."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"643","DOI":"10.1038\/ejcn.2014.40","article-title":"Body composition changes in pregnancy: Measurement, predictors and outcomes","volume":"68","author":"Widen","year":"2014","journal-title":"Eur. J. Clin. Nutr."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"89","DOI":"10.5830\/CVJA-2016-021","article-title":"Physiological changes in pregnancy","volume":"27","author":"Catherine","year":"2016","journal-title":"Cardiovasc. J. Afr."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1505","DOI":"10.1007\/s00484-022-02301-6","article-title":"Physiological mechanisms of the impact of heat during pregnancy and the clinical implications: Review of the evidence from an expert group meeting","volume":"66","author":"Samuels","year":"2022","journal-title":"Int. J. Biometeorol."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"341","DOI":"10.1038\/sj.jp.7211290","article-title":"Amniotic Fluid: Not Just Fetal Urine Anymore","volume":"25","author":"Underwood","year":"2005","journal-title":"J. Perinatol."},{"key":"ref_14","unstructured":"Fitzsimmons, E.D., and Bajaj, T. (2025, October 13). Embryology, Amniotic Fluid, StatPearls, Available online: http:\/\/www.ncbi.nlm.nih.gov\/books\/NBK541089\/."},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Obuchowska, A., Standy\u0142o, A., Kimber-Trojnar, \u017b., and Leszczy\u0144ska-Gorzelak, B. (2021). The Possibility of Using Bioelectrical Impedance Analysis in Pregnant and Postpartum Women. Diagnostics, 11.","DOI":"10.3390\/diagnostics11081370"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"357","DOI":"10.3109\/10641950903116523","article-title":"Bioimpedance in pregnant women with preeclampsia","volume":"29","author":"Hirakawa","year":"2010","journal-title":"Hypertens. Pregnancy"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"578","DOI":"10.1093\/ajcn\/59.3.578","article-title":"Total body water in pregnancy: Assessment by using bioelectrical impedance","volume":"59","author":"Lukaski","year":"1994","journal-title":"Am. J. Clin. Nutr."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"171","DOI":"10.1016\/S0301-2115(01)00330-X","article-title":"Bioelectrical impedance analysis during pregnancy and neonatal birth weight","volume":"98","author":"Ghezzi","year":"2001","journal-title":"Eur. J. Obstet. Gynecol. Reprod. Biol."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"e14098","DOI":"10.5812\/ijem.14098","article-title":"Hormones and hemodynamics in pregnancy","volume":"12","author":"Tkachenko","year":"2014","journal-title":"Int. J. Endocrinol. Metab."},{"key":"ref_20","first-page":"e40725","article-title":"Renin-Angiotensin System: Updated Understanding and Role in Physiological and Pathophysiological States","volume":"15","author":"Kanugula","year":"2023","journal-title":"Cureus"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"193","DOI":"10.1515\/jpme.1983.11.4.193","article-title":"Colloid osmotic pressure: Variations in normal pregnancy","volume":"11","author":"Wu","year":"1983","journal-title":"J. Perinat. Med."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"198","DOI":"10.1093\/cvr\/cvq062","article-title":"Microvascular fluid exchange and the revised Starling principle","volume":"87","author":"Levick","year":"2010","journal-title":"Cardiovasc. Res."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"R847","DOI":"10.1152\/ajpregu.00506.2015","article-title":"Relaxin deficiency attenuates pregnancy-induced adaptation of the mesenteric artery to angiotensin II in mice","volume":"310","author":"Marshall","year":"2016","journal-title":"Am. J. Physiol. Regul. Integr. Comp. Physiol."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"851","DOI":"10.1016\/j.amjhyper.2004.12.019","article-title":"Natriuretic response to direct renal interstitial volume expansion (DRIVE) in pregnant rats","volume":"18","author":"Yu","year":"2005","journal-title":"Am. J. Hypertens."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"69","DOI":"10.1016\/j.ejogrb.2016.07.502","article-title":"Maternal body fluid composition in uncomplicated pregnancies and preeclampsia: A bioelectrical impedance analysis","volume":"204","author":"Staelens","year":"2016","journal-title":"Eur. J. Obstet. Gynecol. Reprod. Biol."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"117","DOI":"10.2147\/IJWH.S378020","article-title":"Window to the Womb: Amniotic Fluid and Postnatal Outcomes","volume":"15","author":"Whittington","year":"2023","journal-title":"Int. J. Womens Health"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"960","DOI":"10.1093\/ajcn\/80.4.960","article-title":"Hydration of fat-free mass in healthy women with special reference to the effect of pregnancy","volume":"80","author":"Lof","year":"2004","journal-title":"Am. J. Clin. Nutr."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"967","DOI":"10.1152\/japplphysiol.00900.2003","article-title":"Evaluation of bioimpedance spectroscopy for measurements of body water distribution in healthy women before, during, and after pregnancy","volume":"96","author":"Lof","year":"2004","journal-title":"J. Appl. Physiol."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"3128767","DOI":"10.1155\/2020\/3128767","article-title":"Reproducibility of Bioelectrical Impedance Analysis in Pregnancy and the Association of Body Composition with the Risk of Gestational Diabetes: A Substudy of MUMS Cohort","volume":"2020","author":"Bai","year":"2020","journal-title":"J. Obes."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"645","DOI":"10.1038\/s41430-018-0152-8","article-title":"Advances in assessing body composition during pregnancy","volume":"72","author":"Most","year":"2018","journal-title":"Eur. J. Clin. Nutr."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"819","DOI":"10.1111\/bjh.16221","article-title":"UK guidelines on the management of iron deficiency in pregnancy","volume":"188","author":"Pavord","year":"2020","journal-title":"Br. J. Haematol."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"199","DOI":"10.1016\/j.tem.2009.12.008","article-title":"Developmental origins of metabolic disease: Life course and intergenerational perspectives","volume":"21","author":"Godfrey","year":"2010","journal-title":"Trends Endocrinol. Metab."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"1423","DOI":"10.1067\/S0002-9378(03)00596-9","article-title":"Composition of gestational weight gain impacts maternal fat retention and infant birth weight","volume":"189","author":"Butte","year":"2003","journal-title":"Am. J. Obstet. Gynecol."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"235","DOI":"10.1016\/S0002-9378(99)70181-X","article-title":"Maternal body fat and water during pregnancy: Do they raise infant birth weight?","volume":"180","author":"Lederman","year":"1999","journal-title":"Am. J. Obstet. Gynecol."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"e75","DOI":"10.1017\/jns.2022.75","article-title":"Gains in body mass and body water in pregnancy and relationships to birth weight of offspring in rural and urban Pune, India","volume":"11","author":"Rush","year":"2022","journal-title":"J. Nutr. Sci."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"1344","DOI":"10.1016\/S0002-9378(11)91714-1","article-title":"Effect of fat and fat-free mass deposition during pregnancy on birth weight","volume":"167","author":"Villar","year":"1992","journal-title":"Am. J. Obstet. Gynecol."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"127","DOI":"10.1067\/mob.2002.122969","article-title":"A longitudinal study of biochemical variables in women at risk of preeclampsia","volume":"187","author":"Chappell","year":"2002","journal-title":"Am. J. Obstet. Gynecol."},{"key":"ref_38","doi-asserted-by":"crossref","unstructured":"Gyselaers, W., Vonck, S., Staelens, A.S., Lanssens, D., Tomsin, K., Oben, J., Dreesen, P., and Bruckers, L. (2018). Body fluid volume homeostasis is abnormal in pregnancies complicated with hypertension and\/or poor fetal growth. PLoS ONE, 13.","DOI":"10.1371\/journal.pone.0206257"},{"key":"ref_39","first-page":"1","article-title":"The Association of Maternal Body Composition and Dietary Intake with the Risk of Gestational Diabetes Mellitus during the Second Trimester in a Cohort of Chinese Pregnant Women","volume":"29","author":"Xu","year":"2016","journal-title":"Biomed. Environ. Sci."},{"key":"ref_40","first-page":"96","article-title":"Total Body Water and Intracellular Water Relationships with Muscle Strength, Frailty and Functional Performance in an Elderly Population. A Cross-Sectional Study","volume":"23","author":"Lorenzo","year":"2018","journal-title":"J. Nutr. Health Aging"},{"key":"ref_41","doi-asserted-by":"crossref","unstructured":"Li, X., Xu, D., Zhang, L., Cao, R., Hao, Y., Cui, L., Chen, T., Guo, Y., and Li, J. (2022). Correlation of body composition in early pregnancy on gestational diabetes mellitus under different body weights before pregnancy. Front. Endocrinol., 13.","DOI":"10.3389\/fendo.2022.916883"},{"key":"ref_42","doi-asserted-by":"crossref","unstructured":"He, Y., Huang, C., Luo, B., and Liao, S. (2023). Association between Maternal Body Composition in Second Trimester and Risk of Fetal Macrosomia: A Population-Based Retrospective Study in China. Nutrients, 15.","DOI":"10.3390\/nu15183879"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"2695","DOI":"10.1080\/14767058.2020.1797666","article-title":"Measuring maternal body composition by biomedical impedance can predict risk for gestational diabetes mellitus: A retrospective study among 22,223 women","volume":"35","author":"Zhang","year":"2022","journal-title":"J. Matern.-Fetal Neonatal Med."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"77","DOI":"10.20463\/pan.2025.0017","article-title":"Association between extracellular-to-intracellular water ratio and type 2 diabetes mellitus in Korean males aged 19\u201380 years: Analysis of KNHANES 2022\u20132023","volume":"29","author":"Lee","year":"2025","journal-title":"Phys. Act. Nutr."},{"key":"ref_45","doi-asserted-by":"crossref","unstructured":"Schoeller, D.A. (2005). Hydrometry. Human Body Composition, Human Kinetics. [2nd ed.].","DOI":"10.5040\/9781492596950.ch-003"},{"key":"ref_46","first-page":"E585","article-title":"Relative dilution spaces of 2H- and 18O-labeled water in humans","volume":"267","author":"Racette","year":"1994","journal-title":"Am. J. Physiol."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"284","DOI":"10.1159\/000243203","article-title":"Total body water measurement in normal and diabetic pregnancy: Evidence for maternal and amniotic fluid equilibrium","volume":"57","author":"Denne","year":"1990","journal-title":"Biol. Neonate"},{"key":"ref_48","first-page":"E153","article-title":"Estimating body composition in late gestation: A new hydration constant for body density and total body water","volume":"268","author":"Catalano","year":"1995","journal-title":"Am. J. Physiol."},{"key":"ref_49","first-page":"543","article-title":"Assessment of change in hydration in women during pregnancy and postpartum with bioelectrical impedance vectors","volume":"23","author":"Lukaski","year":"2007","journal-title":"Nutr. Burbank Los Angel. Cty. Calif"},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"256","DOI":"10.1016\/0002-9343(59)90346-8","article-title":"Anatomy of body water and electrolytes","volume":"27","author":"Edelman","year":"1959","journal-title":"Am. J. Med."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"1037","DOI":"10.1152\/jappl.1995.78.3.1037","article-title":"Fluid changes during pregnancy: Use of bioimpedance spectroscopy","volume":"78","author":"Kopp","year":"1995","journal-title":"J. Appl. Physiol."},{"key":"ref_52","doi-asserted-by":"crossref","unstructured":"Chumlea, W.C., and Sun, S.S. (2005). Bioelectrocal Impedance Analysis. Human Body Composition, Human Kinetics. [2nd ed.].","DOI":"10.5040\/9781492596950.ch-006"},{"key":"ref_53","unstructured":"Heyward, V.H., and Wagner, D.R. (2004). Bioelectrical Impedance Analysis Method. Applied Body Composition Assessment, Human Kinetics."},{"key":"ref_54","first-page":"1226","article-title":"Bioelectrical impedance analysis\u2014Part I: Review of principles and methods","volume":"23","author":"Kyle","year":"2004","journal-title":"Clin. Nutr. Edinb. Scotl."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"100839","DOI":"10.1016\/j.irbm.2024.100839","article-title":"Body Water Volume Estimation Using Bio Impedance Analysis: Where Are We?","volume":"45","author":"Gautier","year":"2024","journal-title":"IRBM"},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"371","DOI":"10.1007\/s11154-022-09764-3","article-title":"Phase angle as an index of physiological status: Validating bioelectrical assessments of hydration and cell mass in health and disease","volume":"24","author":"Lukaski","year":"2023","journal-title":"Rev. Endocr. Metab. Disord."},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"154","DOI":"10.1016\/j.ejogrb.2025.01.008","article-title":"Comparison of body composition change, measured with bioelectrical impedance analysis, between singleton and twin pregnancy: A prospective cohort study","volume":"306","author":"Choi","year":"2025","journal-title":"Eur. J. Obstet. Gynecol. Reprod. Biol."},{"key":"ref_58","doi-asserted-by":"crossref","first-page":"604","DOI":"10.1038\/s41430-021-00990-7","article-title":"Bioelectrical Impedance Vector Analysis (BIVA) for the monitoring of body composition in pregnancy","volume":"76","author":"Moroni","year":"2022","journal-title":"Eur. J. Clin. Nutr."},{"key":"ref_59","first-page":"55","article-title":"Vectores de impedancia bioel\u00e9ctrica para analizar la composici\u00f3n corporal de mujeres mexicanas embarazadas","volume":"21","year":"2016","journal-title":"Rev. Espec. M\u00e9d.-Quir."}],"container-title":["Nutrients"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-6643\/18\/7\/1031\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,3,26]],"date-time":"2026-03-26T13:53:38Z","timestamp":1774533218000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-6643\/18\/7\/1031"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,3,24]]},"references-count":59,"journal-issue":{"issue":"7","published-online":{"date-parts":[[2026,4]]}},"alternative-id":["nu18071031"],"URL":"https:\/\/doi.org\/10.3390\/nu18071031","relation":{},"ISSN":["2072-6643"],"issn-type":[{"value":"2072-6643","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,3,24]]}}}