NITRIC-OXIDE METABOLITES AND PRETERM PREGNANCY COMPLICATIONS

OBJECTIVE: Intraamniotic infection may play a significant role in pret erm labor and premature rupture of membranes. Synthesis of nitric oxid e and its metabolites nitrite and nitrate purportedly are increased in infection. This project was designed to evaluate whether plasma or ur ine nitrate concentrations are increased in patients with either prete rm labor or premature rupture of membranes in comparison with pregnant controls. STUDY DESIGN: A total of 42 patients between 24 and 35 week s' gestation (20 with preterm labor; 14 with premature rupture of memb ranes, and 8 with premature rupture of membranes and contractions) and 35 additional patients without preterm labor or premature rupture of membranes (controls) had blood and urine collected for nitrate determi nation. Nitrate was reduced to nitrite and quantitated with the Griess reagent. RESULTS: The urine nitrate concentrations were significantly higher only in the preterm labor group compared with the control grou p (1.23 +/- 0.22 vs 0.67 +/- 0.05 mu mol/mg creatinine, p < 0.05). The plasma nitrate level, however, was significantly higher in both the p reterm labor and the premature rupture of membranes groups compared wi th the control group (52.47 +/- 10.11 and 40.05 +/- 5.38 mu mol/L vs 1 6.29 +/- 2.89 mu mol/L, p < 0.05). However, the concentrations of nitr ate in the urine or plasma did not correlate with time from admission to delivery (p > 0.2). Finally, the presence of positive cervical or u rine cultures, a clinical examination consistent with chorioamnionitis , or a maternal temperature >100.4 degrees F was not associated with h igher levels of nitrates in this small series of patients. CONCLUSION: Patients with preterm labor or premature rupture of membranes do have increased nitrate concentrations; however, this increased concentrati on is not predictive of impending delivery but may indicate that a sub clinical infectious process is occurring.