Vasectomy is the surgical interruption of the two tubes (vas deferens) that carry a man's sperm from his testicles to his ejaculatory ducts, where the sperm are stored before departure from his body during orgasm. Vasectomy prevents sperm from being added to the man's ejaculation fluid (semen); therefore, he can no longer make a woman pregnant. The sperm containing fluid that is blocked by vasectomy constitutes only 3% of a man's semen volume, therefore, a man will not notice any changes in his semen. Vasectomy is simply an effective, inexpensive, easy-to-perform method of contraception. Over 500,000 men in North America choose vasectomy each year.