Serum nitric oxide metabolites as a predictive factor of premature delivery

In spite of medical progress in evolving diagnostic methods and clinical treatment premature delivery still remains the main problem in obstetric and perinatology. Nitric oxide (NO) is one of the factors which can be important in physiological mechanisms of placental angiogenesis and regulation of vascular tone and could be useful in predicting the risk of premature labor.

The aim of this study was to establish the relation between NO concentration in serum and uterine activity before 37 weeks of gestation in pregnancy with premature delivery. Correlations between serum level of NO and hemoglobin, C- reactive protein (CRP) and total leukocyte count (TLC) were also studied.

The examined group included 47 primigravidas between 23 and 37 weeks of gestation with diagnosis of premature delivery and 26 gestational age-matched women with uncomplicated pregnancy. Serum NO concentration was determined by colorimetric method using a commercially available kit. In this assay total nitrite (nitrites + nitrates) - was analyzed as indicator of NO production.

As compared to the control group, the maternal serum concentrations of NO in each group of women with premature delivery were lower and these differences were statistically significant (p<0.05). The lowest concentration of NO was observed in the group of patients with spontaneous uterine activity and without premature rupture of membranes (PROM) in comparison to other groups with imminent premature delivery and to the control group. The levels of hemoglobin and CRP were within the physiological range and correlated positively with the concentrations NO (r=0.635, p=0.015; r=0.484, p=0.035 respectively) in all women included in the study.

The decreased level of NO in patients with preterm labor was not connected with subclinical infections but it may be associated with initiation of uterine contraction before 37 weeks of gestation.