Nitric oxide in the uteroplacental, fetoplacental, and peripheral circulations in preeclampsia

Objective: Altered production of nitric oxide by the vascular endothelium m ay influence the pathogenesis of preeclampsia. The aim of this study was to measure circulating levels of nitric oxide metabolites (nitrites) in the u teroplacental, fetoplacental, and peripheral circulation of preeclamptic pr egnancies compared-with normotensive controls. Methods: Fifteen women with preeclampsia were compared with 16 women with n ormotensive pregnancies. At cesarean, blood samples were taken from the ute rine vein draining the placental site, the umbilical vein, and the antecubi tal vein after delivery of the baby but before delivery of the placenta. Pl asma nitrites were measured using the Greiss reaction after conversion of p lasma nitrates to nitrites using nitrate reductase. Results: Nitric oxide metabolites were higher in the uteroplacental (P < .0 1), fetoplacental (P < .001), and peripheral (P < .02) circulations in samp les from preeclamptic pregnancies compared with control pregnancies. In sam ples from the fetoplacental circulation only, nitric oxide metabolite level s were negatively correlated with gestational age (r = -.489, P < .01) and birth weight (r = -.544, P < .004). Nitric oxide metabolite levels were not significantly correlated with blood pressure, placental weight, or materna l age. Conclusion: In established preeclampsia, production of nitric oxide was hig her in the uteroplacental, fetoplacental, and peripheral circulation than i n normotensive pregnancies. This increase may be part of a compensatory mec hanism to offset the pathologic effects of preeclampsia. (Obstet Gynecol 19 99;93:958-63. (C) 1999 by The American College of Obstetricians and Gynecol ogists.)