FLUID CHANGES DURING PREGNANCY - USE OF BIOIMPEDANCE SPECTROSCOPY

The increase in body water during pregnancy is responsible for the lar gest portion of weight gain and is of interest to clinical practitione rs. However, assessing changes in body fluids is not easily accomplish ed during pregnancy. The purpose of this study was to examine the accu racy of bioelectrical impedance spectroscopy for estimating fluid volu mes before, during, and after pregnancy. Ten healthy adult women were recruited for the study. Total body water (TBW) and extracellular flui d (ECF) volume were measured at baseline (preconception); 8-10, 24-26, and 34-36 wk of gestation; and 4-6 wk postpartum by deuterium oxide a nd NaBr dilution, respectively. Estimates of TBW and ECF were also obt ained by bioimpedance spectroscopy (BIS). At baseline, mean values for dilution and BIS estimates of TBW and ECF were 33.2 +/- 4.6 (SD) vs. 31.6 +/- 6.2 liters and 15.2 +/- 1.3 vs. 16.9 +/- 2.3 liters, respecti vely. TBW and ECF estimated by BIS were not significantly different fr om the dilution values at any time point. These results suggest that B IS may be useful in estimating volumes of ECF and TBW during pregnancy .