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