Submitted to: Federation of American Societies for Experimental Biology Conference
Publication Type: Abstract Only
Publication Acceptance Date: 11/10/2006
Publication Date: 4/1/2007
Citation: Lukaski, H.C., Hall, C.B., Siders, W.A. 2007. Validity of bioelectrical impedance vector analysis (BIVA) to assess total body water (TBW) in women before, during pregnancy and post partum (PP) [abstract]. Journal of Federation of American Societies for Experimental Biology. 21(5):A7.
Technical Abstract: Increases in TBW are typical of pregnancy with advancing gestation. Because excessive TBW expansion can lead to adverse outcomes, a safe non-invasive method for routine assessment of TBW would be useful clinically. BIVA uses resistance (R) and reactance (Xc) determined with 800 uA at 50 kHz and normalized for height (H) to establish a vector with length and position; it has been used to monitor hydration status in hemodialysis patients. To ascertain the validity of BIVA in physiological conditions, we studied 15 women, aged 21-37 y, before, during pregnancy and PP. TBW assessed with D2O dilution and body R and Xc determined with single-frequency tetrapolar BIA were measured regularly. Body weight (61.9±2.3 to 75.5±2.3 kg) and TBW (32.7±1.1 to 39.8±1.1 L) increased (p<0.05) from pre-pregnancy to the 3rd trimester of pregnancy, and decreased (p<0.05; 67.0±2.3 kg and 34.0±1.1 L) PP. R/H and Xc/H decreased (p<0.05; 361±10 to 318±10 and 44±1 to 36±1 Ohms/m) during pregnancy and increased (p<0.05; 355±10 and 41±1 Ohms/m) PP. Vector length decreased (p<0.05; 363±10 to 320±10 Ohms) during pregnancy, and increased PP (p<0.05; 357±10 Ohms). Changes in vector length and TBW during pregnancy and PP were correlated (r = - 0.599; p<0.001). These findings indicate that impedance vectors provide quantitative evidence of hydration status during pregnancy, and suggest that the BIVA method is useful in monitoring hydration status in pregnancy.