Nitric oxide does not mediate the vasodilation of early human pregnancy.

Background: In early pregnancy, a substantial drop in arterial blood pressure occurs, that might be attributed to enhanced vascular nitric oxide synthesis. We investigated whether nitric oxide mediates the vasodilation that occurs in early human pregnancy.

Methods: Resting and stimulated forearm vascular resistance were measured (venous occlusion plethysmograph) in six women at 10 +/- 3 weeks of uncomplicated pregnancy and in the same women 7 +/- 5 weeks after elective termination of pregnancy.