Expansion of intravascular volume and fetal outcome in patients with chronic hypertension and pregnancy.

Measurements of blood volume were carried out between 24 and 40 weeks of gestation in 20 multiparous patients with chronic hypertension and pregnancy. Hypertensive patients had both reduced blood volume and infants of smaller weight (p less than 0.01) than nonhypertensive control subjects. There was a significant difference (p less than 0.01) in the degree of blood volume expansion in hypertensive mothers who were delivered of infants who were adequate for gestational age (AGA), term, or premature, compared to those who were delivered of infants who were small for gestational age (SGA) or stillborn. Classification of chronic hypertension during pregnancy according to the American Committee on Maternal Welfare classification or according to severity of the hypertension was of no value in identifying the mothers at risk of delivering intrauterine growth-retarded infants. However, failure in achieving a blood volume expansion of at least 60 c.c. per kilogram clearly identified those pregnancies leading to growth retardation and fetal death. The decrease or lack of intravascular volume expansion was reflected in the presence of creatinine clearance values at nonpregnant levels in the mothers who were delivered of SGA infants and in a significant reduction below the nonpregnant levels in those who were delivered of stillborn infants. These data suggest that measurement of blood volume and endogenous creatinine clearance in patients with chronic hypertension and pregnancy is a useful parameter in the identification of those patients who will have a poor fetal outcome.