Clinical signs of normal plasma volume expansion during pregnancy.

A majority of cases of pregnancy complications are associated with a relative maternal hypovolemia. The records of 200 pregnant women who had had plasma volume determinations were reviewed in hopes of finding indicators of relative maternal hypovolemia other than the pregnancy complication itself. The signs of relative hypovolemia in pregnant women include those of decreased uterine growth, absence of a maternal systolic flow murmur, and absence of significant dependent ankle edema. Laboratory tests indicative of maternal hypovolemia include failure to develop a decline in maternal hematocrit, serum blood urea nitrogen/creatinine ratio greater than 15, a decreased creatinine clearance, abnormal platelet function, elevated serum glutamic oxaloacetic transaminase, ultrasonic evidence of oligohydramnios and/or decreased maternal heart size, and absence of hypervolemia on chest x-ray film. These findings and tests are only relative indicators of maternal hypovolemia, and it is suggested that, for an accurate defining of pregnant women who are at risk, the actual plasma volume determination has to be performed frequently in the pregnant population.