Maternal circulating nitrite levels are decreased in both normal normotensive pregnancies and pregnancies with preeclampsia

Objective: To evaluate whether maternal nitric oxide synthesis in pregnanci es with preeclampsia is different from that in normal normotensive pregnanc ies. Materials: Maternal circulating combined nitrate and nitrite levels or nitrite level were compared between 10 normotensive nonpregnant women, 30 normotensive pregnant women (10 first-trimester, 10 second-trimester, and 1 0 third-trimester pregnancies), 20 normotensive postpartum women (10 at 1 w eek after delivery, and 10 at 4 weeks after delivery), and 13 preeclamptic women (32 to 40 weeks' gestation). End-products of nitric oxide syn thesis were measured from maternal venous blood samples using a fluorometric assay . Results: Maternal circulating nitrite levels in nonpregnant women (1.13 /- 0.22 mu M) were significantly higher than those in the first-trimester p regnant women (0.68 +/- 0.13 mu M), second-trimester pregnant women (0.65 /- 0.13 mu M), third-trimester pregnant women (0.48 +/- 0.17 mu M), first p uerperal week women (0.36 +/- 0.16 mu M), and fourth puerperal week women ( 0.67 +/- 0.17 mu M), respectively (p < 0.05). Maternal circulating nitrite level was decreased with advancing gestation, still remained low just after delivery, and was increased 4 weeks later. There was no significant differ ence in maternal circulating nitrite level between preeclamptic women (0.40 +/- 0.17 mu M) and third-trimester pregnant women (0.48 +/- 0.17 mu M) How ever, there were no significant differences in maternal circulating combine d nitrate and nitrite levels among the groups. Conclusion: These results su ggest that the maternal nitric oxide synthesis is not changed in normal nor motensive pregnancies and pregnancies with preeclampsia. However, plasma ni trite level, which has stronger spasmolytic activity than the activity of t he nitrate, was decreased in both normal normotensive pregnancies and pregn ancies with preeclampsia.