Periodic abstinence is a natural method of contraception in which the couples avoid coitus from day 10 to 17 of the menstrual cycle when ovulation could be expected. Coitus interruptus is another natural method of contraception in which the male partner withdraws his penis from the vagina just before ejaculation so as to avoid insemination. Vasectomy is a surgical (sterilization) method, performed in males. LNG-20 is a hormone-releasing IUD.