Background Total body water (TBW) is one component of fat-free mass and changes in TBW are influenced by fluid shifts (especially during transition to postnatal life), electrolyte balance and nutritional status. Normal values for term-born neonates and preterm infants at birth have not been defined in large cohorts, limiting investigation into its monitoring and use in clinical practice.
Objective To systematically review the evidence base for percentage of TBW in term-born infants, quantify the effect of prematurity on TBW at birth, and describe normal progression of TBW over time in preterm infants.
Methods Systematic review of Medline, Web of Science Core Collection and EBSCO-CINAHL (January 1946 to January 2020). Included articles used dilutional methods to assess TBW.
Results Searches identified 2349 articles of which 22 included data suitable for analysis. Mean TBW in term-born newborns was 73.8% (95% CI 72.47% to 75.06%, 15 studies, 433 infants). Meta-regression showed that TBW was higher in preterm infants (up to 90% at 26 weeks gestation, dropping to 75% at 36 weeks corrected gestation) and was negatively correlated with gestation at birth, falling 1.44% per week (95% CI 0.63% to 2.24%, 9 studies, 179 infants). Analysis of TBW over time during the ex utero growth of preterm infants was not possible due to paucity of data.
Conclusion This review defines the normal TBW percentage in term-born infants and confirms and quantifies previous findings that preterm infants have a higher TBW percentage.
Data availability statement
All data relevant to the study are included in the article. Data enquiries should be made to Aneurin Young (firstname.lastname@example.org).
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Contributors AY contributed to the conception, design, data acquisition, data analysis, data interpretation and drafting of the work. LKB contributed to the acquisition, analysis and interpretation of data. SE contributed to critical revision of the work for important intellectual content. MJJ and RMB contributed to the conception and design of the work, and to critical revision of the work for important intellectual content.
Funding The study was supported by the National Institute for Health Research Biomedical Research Centre Southampton, UK.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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