A serum biochemical profile of normal pregnancy

Abstract

Serum sodium, potassium, chloride, magnesium, calcium, phosphate, urea, urate, creatinine, carbon dioxide, total alkaline phosphatase, total protein and albumin levels during pregnancy were studied in groups of subjects at less than 14 weeks' gestation, at 14-20 weeks, at 20-28 weeks and at 36-40 weeks. These were compared with levels in a nonpregnant control group matched for age and sex. Serum potassium, sodium and chloride levels remained within the normal range, while calcium, phosphate, total protein and albumin levels decreased progressively after the first trimester. Magnesium levels decreased progressively from early pregnancy to term, and urea, creatinine and carbon dioxide levels all decreased markedly throughout pregnancy. Urate levels were markedly decreased in early pregnancy but returned to normal at term, and the alkaline phosphatase values demonstrated the expected marked increase to term. The fact that all these values were not equally affected suggests that haemodilution cannot be held responsible for all serum changes during pregnancy. Individual results are discussed and a biochemical profile is suggested.