Fetal lactic dehydrogenase variation in normal pregnancy and in cases of severe intra-uterine growth restriction.

Physiological and pathological fetal levels of lactic dehydrogenase (LDH), including its five different iso-enzymes are still poorly known. Our objectives were to compare total LDH levels and its five iso-enzymes between a control group of healthy fetuses and a group of fetuses with severe intra-uterine growth restriction (IUGR), and to determine the biochemical associations and the prognostic value of elevated LDH activity in fetuses with IUGR. Total LDH levels, haematologic values and liver enzyme activities were measured in 108 healthy fetuses from 17 to 37 weeks of gestation and in 44 fetuses with severe IUGR. Total fetal LDH in plasma from the healthy fetuses were constant throughout pregnancy (mean (SD)= 305.09 (46.97)). Total LDH values in plasma significantly increased in cases of IUGR (p=0.003), and the degree of increase was significantly correlated with fetal erythroblastosis (n =44, r=0.80, p<0.001). LDH 5 significantly decreased in the IUGR group (p=0.03). Total LDH values strictly above 400 IU/l (a value equal to the mean+2 SD in the healthy fetus group) were found to be significantly associated with thrombocytopenia (p<0.001), erythroblastosis (p=0.008) and an increase in AST value (p=0.03). These results suggest that the fetal LDH value in plasma is a useful biological marker for severe chronic distress.