Maternal plasma and amniotic fluid angiogenic factors and their receptors in monochorionic twin pregnancies complicated by twin‐to‐twin transfusion syndrome

Objective Angiogenic factors play a role in human placentation and may be aberrant in severe twin‐to‐twin transfusion syndrome (TTTS). The aim of this study was to investigate the maternal plasma and amniotic fluid angiogenic factor and receptor concentrations in twin pregnancies complicated by TTTS and to evaluate the effects of fetoscopic laser ablation. Methods A prospective cohort of monochorionic (MC) twins complicated by severe TTTS (n = 23) was studied between October 2006 and December 2007. A cohort of uncomplicated dichorionic (DC) (n = 12) and MC (n = 7) pregnancies were studied for comparison. Circulating angiogenic factors and their receptors were measured in the maternal plasma and the recipient twin's amniotic fluid by enzyme‐linked immunosorbent assay and/or FAST Quant human angiogenesis array. Results Plasma vascular endothelial growth factor (VEGF)‐C concentrations were significantly lower in TTTS than in uncomplicated twin pregnancies (P < 0.0001). In contrast, plasma angiopoietin (Ang)‐2 levels and the ratio of soluble vascular endothelial growth factor receptor‐1 (sVEGFR‐1) to placental growth factor (PlGF) levels were significantly increased in TTTS (P < 0.01). Plasma VEGF‐D was significantly increased in advanced stage TTTS (Stage III/IV cohort; P < 0.01). This was independent of fetal size, amniotic fluid volumes or the number of apparent placental arteriovenous anastomoses. In TTTS pregnancies, amniotic fluid VEGF‐C, VEGF‐A, Ang‐1 and the sVEGFR‐1/PlGF ratio were increased compared to paired maternal plasma concentrations (P < 0.0001) while amniotic fluid concentrations of PlGF, Ang‐2 and soluble tyrosine kinase with immunoglobulin‐like/epidermal growth factor‐like domains 2 (sTie‐2) were significantly lower than plasma concentrations (P < 0.0001). No significant association between maternal plasma and amniotic fluid concentrations of angiogenic factors was noted. Plasma PlGF was transiently decreased after fetoscopic laser ablation, returning to baseline by 1 week (P = 0.0314). Fetoscopic laser ablation also affected plasma sVEGFR‐1/PlGF ratio with a transient increase after therapy, followed by a significant reduction to below basal concentrations by 1 week (P = 0.0102). Only VEGF‐D was significantly different (+8.3%; P = 0.0155) in amniotic fluid immediately after the completion of fetoscopic laser ablation. Conclusion Maternal angiogenic activity is decreased in severe TTTS, with an increased sVEGFR‐1/PlGF ratio and concentratio