Production of prostacyclin, 6-keto-PGF1 alpha and thromboxane B2 by human umbilical vessels increases from the placenta towards the fetus.

The aim of this study was to investigate the production of prostacyclin (PGI2) and thromboxane B2 (TXB2) by incubated samples of umbilical arteries and veins taken at different distances (2, 10, 20, 30 cm) from the placenta to provide additional information relevant to the haemodynamics of umbilical blood flow. The production of PGI2, and 6-keto-PGF1 alpha (the stable metabolite of PGI2), was higher in both veins and arteries as the distance from the placenta at which the vessels were sampled was increased. A similar correlation between production by venous rings and distance from the placenta was observed for TXB2, but there was no apparent gradient of TXB2 production by the samples of arterial rings. No statistically significant variations were discernible in the ratio of 6-keto-PGF1 alpha:TXB2 (approximately 50 in the veins and approximately 20 in the arteries) in relation to the sampling distance. The significance of these high ratios is discussed in relation to umbilical blood flow and fetal well-being and development.