Maternal and fetal serum nitric oxide (NO) concentrations in normal pregnancy, pre-eclampsia and eclampsia

To measure the maternal and fetal serum concentrations of total nitrites and nitrates (as an index of nitric oxide production) in normal pregnancy, pre-eclampsia and eclampsia.

Three groups of women were studied cross-sectionally: late pregnant women with pre-eclampsia and eclampsia (n=31); normal late pregnant women (n=32); and age-matched healthy non-pregnant women (n=21). Venous blood samples were collected from all women and both maternal and umbilical venous samples were collected from pregnant women.

Blood samples were assayed for nitric oxide (NO) production by Greiss reaction which measures the combined oxidation products of NO (total nitrites and nitrates).

There was a significant increase in serum total nitrites and nitrates concentrations in normal pregnant women than in the serum of age-matched normal non-pregnant women (P<0.0001). Significantly higher total nitrites and nitrates levels were found in the maternal sera of the pre-eclamptic and eclamptic women compared with those of normal pregnant women (P<0.0001). Also, fetal blood levels of total nitrites and nitrates were significantly increased in pre-eclampsia and eclampsia compared with those of normal pregnancy (P<0.0001).

(1) Serum nitric oxide (NO) production is increased in normal pregnancy than in the normal non-pregnancy. (2) Maternal and fetal serum NO levels are increased significantly in pre-eclampsia and eclampsia, which possibly represents a compensatory/protective mechanism to maintain blood flow and limit platelets aggregation in the fetal-maternal circulations. (3) The increase in NO production is directly related to the severity of pre-eclampsia; this would be of diagnostic significance for the prediction of the severity of this syndrome.