Severing the ductus deferens is the primary means of male sterilization for humans. The process, known as a vasectomy, is a relatively simple and safe surgical procedure that is often completed in less than 15 minutes. The ductus deferens is also sometimes the cause of natural sterility in men. Indeed, congenital bilateral absence of the vas deferens (CBAVD) is reportedly the cause of as many as 5 percent of all cases of male infertility. Associated with a mutated gene related to cystic fibrosis, the recessive condition may be passed onto offspring if a male with CBAVD utilizes medical procedures to enable him to have his own biological children.