Blood chemistry of normal human fetuses at midtrimester of pregnancy.

Thirteen biochemical parameters and five enzymatic activities were determined on sera of 63 normal human fetuses sampled by direct puncture under ultrasound guidance, between the 20th and the 26th wk of gestation, and on their mothers. They were referred to us for various prenatal diagnoses but were well and confirmed healthy at birth. Some parameters were found to be very similar in both groups, mainly creatinine, calcium, creatine kinase, aspartate aminotransferase, and gamma-glutamyl transferase. Some values were significantly higher in the fetuses, such as total bilirubin, direct bilirubin, phosphorus, lactic dehydrogenase and alkaline phosphatase activities, and alpha-fetoprotein. Urea, uric acid, glucose, triglycerides, cholesterol, total protein, and albumin levels were found to be lower in fetuses. These data indicate a slower metabolism in fetuses compared to their mothers, a lower level of energy requirement, and a relative liver immaturity. These normal values of fetal biochemistry will improve our knowledge of physiology and help to determine the specific values of a test in fetal pathology.