METABOLIC STUDIES IN PREGNANCY AND THE PUERPERIUM*

Abstract

Metabolic balance studies, determinations of body fluid compartments and measurement of urinary corticosteroid excretion were carried out in 5 pregnant women during the latter part of gestation and immediately post partum. During the study significant storage of nitrogen and potassium and expansion of extracellular volume occurred in the antepartum period. The accelerated weight loss following delivery may have been in part associated with the restoration of body fluid compartments to normal. Negative nitrogen and potassium balances were observed at this time, associated with a rise in the levels of serum nonprotein nitrogen and potassium. Sodium storage was most marked in the antepartum period, and continued to a lesser degree in the postpartum period when the overall sodium balance was considered for this part of the study. Sodium diuresis was always observed soon after delivery. The establishment of a new metabolic equilibrium had not occurred by the time of cessation of these studies. In the antepartum period there was an apparent correlation between sodium retention and aldosterone excretion. Immediately post partum, variations in sodium excretion were also associated with changes in aldosterone excretion, but later in the postpartum period aldosterone excretion returned to nonpregnant levels and did not vary with further changes in the sodium balance. An increase in total blood volume, extracellular fluid volume, plasma volume, and total body water was observed in the antepartum period. There was a postpartum reduction in these parameters, and the data suggest that it may have been partly due to the alterations in aldosterone secretion.