ABSTRACT
INTRODUCTION: The vascular endothelium is thought to be responsible for cardiovascular adaptations in gestation, such as the decrease in peripheral vascular resistance and the decrease in arterial pressure. There is an increase of nitric oxide (NO) serum levels in normal gestation due to an increment in the activity of the enzyme endothelial nitric oxide synthase (eNOS). OBJECTIVES: To compare maternal flow-mediated dilation of the brachial artery (FMD) and the nitrite concentration between the third trimester of pregnancy and postpartum period. Additionally we want to evaluate whether FMD correlates with nitrite concentration. METHODS: Eligibility criteria were healthy pregnant women with single fetus, gestational age greater than 28 weeks, nonsmokers, and without personal or family history of vascular disease. Each pregnant woman was examined in the third trimester of pregnancy (3(rd)T) and between 8 and 12 weeks postpartum (PP) to evaluate FMD and nitrite concentrations in the whole blood. We excluded women who were not examined in both periods. We compared the values between the two periods using paired t tests. The correlation between FMD and nitrite concentration was examined by Pearson correlation coefficient. Significance level was set at p<0.05. RESULTS: 42 pregnant women were invited for the study. 35 healthy women were elected and 7 of them were excluded for not attending the postpartum evaluation. We found a trend of decreased FMD in the PP period (10.39±5.57 % vs. 8.42±4.21 %, p=0.11; 3(rd)T vs. PP respectively). No significant change was observed in the nitrite concentration (257.41±122.95nmol/L vs.237.16±90.01nmol/L, p=0.28). We did not observe significant correlation between FMD and nitrite during 3(rd)T (r=-0.13, p=0.50) or PP (r=0.14, p=0.48). CONCLUSION: Although our sample size did not permit sufficient precision, FMD seems to decrease between the third trimester and postpartum period. Nitrite concentration did not change between the third trimester of pregnancy and the postpartum period, and it was not correlated to FMD. Studies evaluating larger samples are necessary to confirm these findings.