Subincision is a form of body modification consisting of a urethrotomy, in which the underside of the penis is incised and the urethra slit open lengthwise, from the urethral opening (meatus) toward the base. The slit can be of varying lengths. Disadvantages include the risk of surgery, which is often self-performed, and increased susceptibility to sexually transmitted infections (STIs). Among heterosexual men, the ability to impregnate (specifically, getting sperm into the vagina) may also be decreased.