Nitric oxide production increases during normal pregnancy and decreases in preeclampsia.

To investigate the changes in nitric oxide (NO) production during and after normal pregnancy and in pregnancies complicated by preeclampsia, we measured serum nitrates and nitrites (NOx) concentrations and serum iron markers in 347 subjects. Serum NOx concentrations were determined after reduction of nitrates to nitrites using the Griess reaction. Serum iron and serum ferritin were assayed using an automatic chemical analyzer and a chemiluminescence method. Serum NOx concentrations were significantly higher in the first trimester (117.3 +/- 31.4 microM) than in nonpregnant women (23.8 +/- 7.1 microM). High NOx concentrations persisted throughout normal pregnancy, irrespective of serum ferritin concentrations, and returned to nonpregnant levels by 9-12 wk postpartum. Mean NOx concentrations in preeclamptic women were 43.1 +/- 12.7 microM, which were significantly lower than those in the gestation age-matched normal pregnant women (249.7 +/- 51.3 microM). In summary, NO production increases with advancing gestation during normal pregnancy and decreases in preeclampsia, regardless of serum ferritin concentrations. Elevated NOx concentrations during pregnancy return to normal within 12 wk after delivery.