Vascular Adaptations in Pregnancy: The Critical Role of Endothelial Function and Nitric Oxide in Maternal-Fetal Health

Background: Endothelial dysfunction is a critical factor in hypertensive disorders of pregnancy, such as preeclampsia. This study aimed to evaluate the role of endothelial function, nitric oxide (NO), and endothelin-1 (ET-1) in normotensive and hypertensive pregnancies to understand the underlying vascular adaptations. Methods: A cross-sectional study was conducted at LUMHS, Jamshoro, from October 2023 to June 2024. A total of 120 pregnant women were divided into normotensive (n=60) and hypertensive (n=60) groups. Participants included pregnant women aged 18 to 40 years with singleton pregnancies between 20 and 36 weeks of gestation. Participants were recruited using a purposive sampling technique from the Obstetrics and Gynecology Department. Serum NO and ET-1 levels were measured, and endothelial function was assessed using flow-mediated dilation (FMD). Data analysis using SPSS 26.0 involved descriptive statistics, independent t-tests for NO and FMD comparisons, chi-square tests for categorical variables, and multivariate regression to adjust for confounders such as maternal age, BMI, and gestational age. Results: Hypertensive women had lower NO levels (24.98 ± 4.72 vs. 34.23 ± 4.54 µmol/L) and FMD values (6.09 ± 1.55% vs. 10.14 ± 1.49%), and higher ET-1 levels (4.46 ± 0.72 vs. 2.52 ± 0.48 pg/mL) than normotensive women (all p < 0.0001). NO correlated positively with FMD (r = 0.61), while ET-1 correlated negatively with NO (r = -0.55) and FMD (r = -0.69). Multiple regression identified NO and ET-1 as significant FMD predictors. Conclusion: Endothelial dysfunction in hypertensive pregnancies is characterized by reduced NO levels, elevated ET-1 levels, and impaired FMD.