During normal pregnancy, blood volume increases by 40 percent, and this increase correlates positively with infant birth weight. The expansion starts in the first trimester, reaches a peak at about 30 weeks gestation, and remains elevated to term. Low maternal blood volume is associated with complications such as pre-eclampsia and intrauterine growth restriction (IUGR). Total body water (intracellular and extracellular) also increases significantly during normal pregnancy, accounting for 60 to 70 percent of the weight gain after the first 20 weeks of pregnancy. The expansion in plasma volume is part of the generalized increase in all compartments of total body water and results from fluid retention rather than a shift within the extracellular fluid compartments.
Was this article helpful?