Objective: To investigate the concentrations of free plasma vascular endothelial growth factor (VEGF) in the maternal and foetal circulations of normal term pregnancies.
Methods: Free plasma VEGF was measured from plasma of umbilical cord and maternal blood by ELISA for each of 20 normal pregnancies delivering at term at an altitude of 3100 m. Spearman's correlation coefficient was used to test for correlation between values and clinical maternal and neonatal data. Student's 't' test was used to test for differences between samples from male and female neonates.
Results: Free plasma VEGF was undetectable from maternal samples, but it was detectable in the cord blood (mean, 560.3775 pg/ml, median, 145.84 pg/ml, range, 22.56-2653.5). No differences were found between neonates sex, and no correlation was found with clinical maternal and neonatal data.
Conclusion: Circulating VEGF is usually bound to the soluble form of its receptor 1 (sFlt-1). High levels of sFlt-1 are secreted by the syncytiotrophoblast during pregnancy, and so free plasma VEGF is undetectable in the maternal circulation. In contrast, our findings are the first to show free plasma VEGF in the umbilical circulation. We speculate that this free VEGF may promote angiogenesis in the foetus and placenta. Our data imply that sFlt-1 is not present in the cord blood, and that secretion by the syncytiotrophoblast is polarised to its apical surface. Further investigations are required to test this hypothesis.