Does Endothelial Nitric Oxide Synthase Gene Variation Play a Role in the Occurrence of Hypertension in Pregnancy?

Objective: Nitric oxide is suggested to play a role in the development of preeclampsia. Methods: We studied 61 patients with gestational hypertension (GH), 77 with GH and significant proteinuria (urine protein excretion ≥ 300 mg 24 h), 82 with essential hypertension (EH) and 188 normotensive women with at least one normal pregnancy. Main Outcome Measure(s): A polymorphism within the constitutive endothelial nitric oxide synthase (ecNOS) gene in various types of hypertension in pregnancy was explored. Results: Allelic and genotypic frequencies did not differ between controls and case groups. A significant difference was observed between the frequency of the rare allele in GH patients and that in EH group (χ2: 4.47, P < .04). This difference approximated the significance when GH subjects with or without proteinuria were grouped (χ2 square: 3.33; P = .068). Cigarette smoking or gravidity did not interact with the ecNOS polymorphism in identifying different types of hypertension in this setting. Conclusion: Our findings argue against an association between ecNOS polymorphism and preeclampsia and support the hypothesis for a different pathogenesis of GH in respect to EH.