Objective: To assess soluble fms-like tyrosin kinase 1 (sFlt-1), free vascular endothelial growth factor (f-VEGF) and the f-VEGF/sFlt-1 quotient in twin pregnancies, and to determine if they are impaired in discordant twins.
Methods: Case-control study between 18 discordant and 46 concordant twin pregnancies. Angiogenic growth factors were measured in maternal serum during pregnancy and in umbilical artery and vein at birth.
Results: Discordant twins were more often conceived by assisted reproductive techniques than concordant twins. Maternal plasma f-VEGF was significantly lower in discordant twins (p = 0.04). F-VEGF and f-VEGF/sFlt-1 in the whole sample show a significant higher level in concordant twins. When we analyzed umbilical cord angiogenic factors, the smaller twin had a lower f-VEGF/sFlt-1 quotient (p = 0.01). We found no correlations between maternal or umbilical growth factors and placental or fetal weight. No difference was found in veno-arterial levels of angiogenic factors in each twin; however, there was a significant rise in arterial f-VEGF (p = 0.06) in discordant twins.
Conclusion: Mothers of discordant twins have a more anti-angiogenic environment compared to those of concordant twins. We also found an anti-angiogenic environment in the small twin when we compared umbilical vein angiogenic factors against its big co-twin.
Keywords: Angiogenesis; VEGF; hypoxia; sFlt-1; twin pregnancy.