A method of determining hypoxia in fetal scalp blood sampled during labor comprises the determination of total lactate dehydrogenase (LDH) in plasma obtained from the sample. The method can comprise the additional determination of K, Mg, Ca, AST, ALT, lactate in the plasma and/or blood. Increased values of one or more of LDH, Mg, Ca, AST, ALT, lactate are indicative of hypoxia in the fetus. Also disclosed is the use of a plasma separation apparatus in the method.