It maintains a powerful barrier against the entry of sperm into the uterus by keeping the cervical mucus thick and sticky. It also changes the lining of the uterus and makes it more difficult for the fertilized egg to implant. Its value in contraception is due to its ability to block luteinizing hormone, one of the reproductive hormones important in ovulation. The third generation progestins tend to have fewer male-like side effects and possibly may have a better effect on cholesterol levels than earlier progestins. Progestins may be used alone or with estrogen in oral contraceptives.
Perfect use refers to contraceptives that are used correctly each time intercourse occurs.
Research has shown that the four most effective standard female contraceptives are surgical sterilization, the IUD, Norplant implants, and Depo-Provera injections. May be covered by insurance. Less at family planning clinic. May be covered by insurance. None, increases risk.