Exhaled nitric oxide concentration and amniotic fluid nitrite concentration during pregnancy

Abstract
We have assessed fetal and maternal nitric oxide (NO) production in pregnancy. Exhaled NO and amniotic fluid nitrite concentrations were measured by chemiluminescence between 10 and 42 weeks of pregnancy. Exhaled NO concentrations did not alter significantly during gestation. In contrast, there was a significant change in mean amniotic fluid nitrite concentration in late pregnancy (P < 0.001). The finding of decreased amniotic nitrite concentrations after 37 weeks of gestation support the hypothesis that reduced NO production may contribute to increased uterine activity in late pregnancy.