Body Water During Pregnancy: Physiology, Clinical Significance and Assessment Methods: A Narrative Review

Area of Science:

• Physiology
• Maternal-Fetal Medicine
• Body Composition Analysis

Background:

• Total body water (TBW) increases significantly during pregnancy due to physiological adaptations supporting maternal and fetal needs.
• Fluid shifts between extracellular water (ECW) and intracellular water (ICW) impact maternal body composition and biomarker interpretation.
• Current research insufficiently integrates body water regulation and assessment in pregnant populations.

Purpose of the Study:

• To review the physiological regulation of TBW and its compartments throughout pregnancy.
• To critically analyze methods for assessing body water distribution in pregnant women.
• To integrate physiological and methodological insights for better understanding maternal hydration.

Main Methods:

• Narrative review synthesizing current knowledge on body water regulation and assessment.
• Analysis of mechanisms for plasma volume expansion, interstitial fluid accumulation, and tissue hydration.
• Evaluation of stable isotope dilution and bioelectrical impedance techniques (BIA, BIS, BIVA).

Main Results:

• Pregnancy involves complex cardiovascular, renal, and endocrine adaptations affecting TBW, ECW, and ICW.
• Body water dynamics influence fetal growth, hypertensive disorders, and gestational diabetes.
• Stable isotope dilution is the reference method for TBW; bioelectrical impedance methods offer practical longitudinal monitoring.

Conclusions:

• Accurate assessment of maternal body water compartments is vital for clinical and nutritional research during pregnancy.
• Understanding fluid redistribution is key for managing pregnancy complications and optimizing outcomes.
• Integrating physiological knowledge with appropriate assessment tools enhances maternal body composition evaluation.