NITRIC-OXIDE METABOLITE IN PREGNANT-WOMEN BEFORE AND AFTER DELIVERY

Background. During pregnancy, systemic vascular resistance as well as vascular sensitivity to vasoconstrictive agents decreases in pregnant women. Methods and materials. The vascular resistance of the fetus is also maintained in the presence of low blood pressure. We believe that the main factors in this phenomenon are nitric oxide (NO), along with prostaglandin. NO is an unstable compound with a short half-life; it is easily converted to nitrite (NO2) and nitrate (NO3). Since NO canno t be precisely quantified, we measured the NO2 concentration in matern al blood just before and after delivery and compared it with the value s of non-pregnant women. Results. NO2 concentrations in the 13 women w ho received cesarean deliveries under epidural anesthesia were not sig nificantly changed by the anesthesia. Before anesthesia the NO2 concen tration was 216+/-115 pmol/mg protein, and after the induction of anes thesia, but before surgery, it was 218+/-112 pmol/mg protein. The NO2 concentration then fell significantly after the surgery to 174+/-75 pm ol/mg protein (p<0.05). In addition, after vaginal delivery, in 17 oth er patients we observed marked decreases in NO2 concentration, falling from 160+/-82 to 125+/-61 pmol/mg protein (p<0.05). These values were significantly higher than those of nonpregnant women (3.4+/-2.1 mu M, 33+/-22 pmol/mg protein) (p less than or equal to 0.0001). Conclusion . These results suggest that NO contributes to the low vascular resist ance observed in the mother and fetus during pregnancy.