Fetal erythropoietin and endothelin-1: relation to hypoxia and intrauterine growth retardation

BACKGROUND: We have examined whether endothelin-1 (ET-1) and erythropoietin (EPO) in amniotic fluid, and EPO in fetal serum obtained by cordocentesis from fetuses with signs of intrauterine growth retardation (IUGR), were correlated to fetal growth and/or chronic fetal hypoxia. METHODS: Amniotic fluid and fetal serum were obtained by cordocentesis from 28 fetuses suspected to have IUGR and subsequently analyzed for EPO and ET-1 by ELISA. These data were correlated to blood gas results and fetal/maternal parameters at delivery. RESULTS: A novel finding was that ET-1 correlated to PO2 in amniotic fluid. The average level of ET-1 in amniotic fluid was 48.3+/-4.7 pmol/L. The results also showed a correlation between EPO levels in amniotic fluid and EPO in fetal serum. Furthermore, EPO correlated weakly to birth weight at delivery. Children with the lowest birth weights had the highest EPO levels. High EPO values, similarly to ET-1, correlated to low pO2 values. The level of EPO in amniotic fluid was 8.0+/-1.6 mIU/ml and in cord blood 29.5+/-9.6 mIU/ml. CONCLUSIONS: The results indicate that ET-1 levels may be a marker for short-term hypoxia, but not for fetal growth, since ET-1 in amniotic fluid was correlated to PO2 at the time of cordocentesis, but not to birth weight. The results also indicate that EPO levels in amniotic fluid and in fetal cord serum are highly correlated, and thus both can be used as markers for fetal growth and chronic hypoxia before the onset of labor.