Studies on Prostanoid Production in the Umbilicoplacental Circulation

The fetoplacental circulation is a low pressure system with a high vascular prostacyclin to thromboxane (Pc/Tx)synthesis ratio. In intrauterin growth restriction (IUGR) and diabetes the prostanoid balance may be altered. AIMS: To investigate relationships between umbilicoplacental vascular prostanoid synthesis (by incubation of vessel samples), circulatory changes (by Doppler velocimetry of umbilical cord blood flows), structural placental changes (by histomorphology), lipid peroxidation (by cord plasma malondialdehyde) and platelet activation (by cord plasma Tx). RESULTS: IUGR-study: 1) Umbilical cord vascular prostanoid synthesis was lower in growth restricted than in normally grown neonates; 2) No correlation between cord prostanoid synthesis and umbilical artery vascular flow resistance was found. Diabetes studies: 1) The Pc/Tx vascular synthesis ratios were generally lower in diabetes compared with controls; 2) A positive correlation between flow resistance and Pc/Tx ratio was found in the umbilical artery; 3) In the umilicoplacental arterial tree, the vascular production of Px decreased and that of Tx increased towards the periphery; 4) Placental histomorphological lesion were in general associated with a higher vascular Tx synthesis and/or lower Pc/Tx synthesis ratio; 5) In contrast, ischemic villitis was associated with a higher Pc/Tx ratio; 6)Signs of platelet activation, but not lipid peroxidation, were found in fetal plasma of diabetics; 7) A defect vascular prostanoid synthesis capacity was found among diabetics. CONCLUSION: In IUGR the vascular prostanoid synthesis was generally low but not associated with abnormal umbilical cord blood flows. Impaired maternal glucose metabolism was associated with disturbances in the prostanoid equilibrium in fetal blood and umbilicoplacental vessels. These finding indicate endothelial cell pathology and disturbed vessel wall function