Background: Most laboratory parameters change during pregnancy. A serial study of a large number of routine haematological and biochemical blood parameters and biochemical urine parameters was conducted in a group of 66 healthy nulliparous pregnant women, who had an uncomplicated pregnancy.
Methods: Blood samples and 24-h urine samples were obtained at four weeks intervals during pregnancy and at 1 (1P) and 6 (6P) weeks after delivery.
Results: During pregnancy, haemoglobin concentration, haematocrit and erythrocyte count were lower, mean cell volume was not different, and mean cell haemoglobin and mean cell haemoglobin concentration were enhanced. The platelet count during pregnancy was not different from the level at 6P but increased 60% at 1P. Serum ferritin decreased 50% whereas plasma fibrinogen increased 100%. Serum creatinine (-28%), uric acid (-35%) and urea (-40%) concentrations were reduced during pregnancy. The serum concentrations of sodium (-4 mmol/l) and potassium (-0.2 mmol/l) were lower, but serum chloride was unaltered. Serum protein and albumen concentrations declined by 7.8 and 9.4 g/l respectively. The serum concentrations of bilirubin, ALAT, ASAT and gamma-GT remained unaltered. Serum LDH was 30% above normal non-pregnant values at 1P. The heat-stable alkaline phosphatase level increased in the third trimester. Heat-stable and heat-labile fractions were both elevated at 1P. The serum osmolality was 9 mosmol/kg lower and urine volume was about 25% higher during pregnancy. The creatinine excretion was unaltered but creatinine clearance increased by 25%.
Conclusions: The concentrations of most components change during pregnancy. The interpretation of results of laboratory tests in pregnant women should be made with caution.