Nitric oxide concentrations are increased in the fetoplacental circulation in preeclampsia

The aim of this study was to measure serum concentrations of total nitrites, as an index of nitric oxide synthesis, in the maternal and fetal circulations of normal pregnancies and in pregnancies complicated by preeclampsia.

We studied 32 women with preeclampsia and 36 with uncomplicated pregnancies. Maternal venous blood samples were collected from all of the patients, and umbilical venous blood was collected from 13 of the preeclamptic group and 17 of the control group. Serum nitric oxide concentrations were determined with the Greiss reaction by measuring combined oxidation products of nitric oxide, serum nitrite and nitrate after reduction with nitrate reductase.

There were no significant differences in maternal serum nitrite concentrations between the groups (control group 29.8 +/- 1.07 mumol/L, preeclamptic group 29.5 +/- 1.06 mumol/L). Significantly higher serum nitrite concentrations were found in umbilical venous serum in the preeclamptic group compared with the control group (34.59 +/- 1.12 mumol/L vs 23.90 +/- 1.05 mumol/L, p < 0.01).

Total nitrites are increased in the fetoplacental circulation in preeclampsia. These results support the hypothesis that increased nitric oxide production may be a compensatory response to improve blood flow or may play a role in limiting platelet adhesion and aggregation.