Maternal and fetal nitric oxide production in normal and abnormal pregnancy

Abstract

Objectives: To characterize maternal and fetal nitric oxide (NO) production in normal and abnormal pregnancy by measuring nitrate (NO3-) and nitrite (NO2-) metabolites in maternal venous blood, umbilical venous and arterial blood and amniotic fluid. Methods: This was a prospective cross-sectional study in 160 singleton pregnancies: 60 with one complication (infection, n = 37; gestational diabetes, n = 12; pre-eclampsia, n = 11) and 103 normal controls. Nitrate plus nitrite levels were assayed by reduction with Griess reagent. Comparisons were: maternal vs. fetal compartments; normal vs. abnormal pregnancy; and early vs. late pregnancy. Results: Amniotic nitrate and nitrite levels increased from early to late normal pregnancy (20.79 to 28.42 μmol/l, p < 0.02), decreasing slightly at term, and increased from early to late abnormal pregnancy (23.29 to 39.18 μmol/l, p < 0.0001). Late pregnancy levels were higher in abnormal vs. normal pregnancy in amniotic fluid (36.25 vs. 21.70 μmol/l, p = 0.003) and maternal blood (25.80 vs. 18.26 μmol/l, p = 0.002). Overall levels were higher in amniotic fluid than in maternal plasma, and in fetal compartments than in co-sampled maternal plasma (p < 0.005, vs. normal pregnancy). Conclusions: NO metabolite levels increased through normal and particularly abnormal pregnancy, predominantly in the fetal compartments, suggesting that NO production is an additional instrument in the fetal control of the intrauterine environment.