 Worldwide, the incidence of preeclampsia ranges from 2 to 10 of pregnancies. The World Health Organization WHO estimates that the incidence of preeclampsia is seven times higher in developing countries than in developed 2.8 and 0.4. In Mexico it is estimated that preeclampsia - eclampsia is a major cause of maternal and perinatal morbidity and mortality. Because it is an idiopathic heterogeneous syndrome associated with endothelial damage, so far there is no effective treatment to decrease the morbidity and mortality of this entity, so it is necessary to strengthen prevention; the use of aspirin alone is inconclusive, in addition to the information the investigators have reduced the effect of these strategies on arterial stiffness; Moreover, it has been observed that L-arginine lowers blood pressure in this population. It is for this that is of interest to know the efficacy and safety of the combination of L-arginine low dose, which is known as an important eNOS in NO production substrate, and aspirin for its qualities of antiinflammatory and anticoagulant in the prevention of preeclampsia and also determine their effect on arterial stiffness as a noninvasive method, as is the applanation tonometry. 