The active ingredient of Viagra, sildenafil, has passed the second phase of clinical trials as a means to prevent oxygen starvation in children in childbirth, the American Journal of Obstetrics and Gynecology reported . Sildenafil dilates the blood vessels of the placenta and thereby enhances blood flow to the fetus. This reduces the likelihood that the mother will need to have a cesarean section if her baby begins to experience oxygen deficiency during labor. Contraction of the uterus during childbirth reduces the intensity of blood flow through the placenta, so if contractions occur very often and last a long time, you …