How the IUD Works for Birth Control

Copper IUD

The copper IUD (ParaGard) changes the lining of the uterus so implantation cannot take place. According to Family Health International, ParaGard may be used effectively as an emergency form of birth control if inserted within five days, as a fertilized egg cannot implant successfully. The copper IUD releases a small amount of copper, which inactivates sperm in the cervix. The copper IUD is effective for up to 10 years.

Hormonal IUD

The hormonal IUD Mirena releases small amounts of progestin, which prevents ovulation. In addition, according to Planned Parenthood, progestin thickens the cervical mucus, which in turn blocks the movement of sperm. The shape of the IUD impedes the sperm from entering the fallopian tubes. Hormonal IUDs are left in place for up to five years.

Both IUD Types

Both types of IUD change the uterus lining, making implantation of a fertilized egg less likely. Planned Parenthood states that both affect the movement of sperm, making the sperm unable to join with an egg. Both types of IUD are available in the United States by prescription, and both are inserted into the uterus by a physician and remain in place for years. The Mayo Clinic states that it is important to note that while the IUD is an effective means of birth control, neither type of IUD is effective in preventing sexually transmitted diseases.