How it Works
Both IUDs are effective because of their ability to immobilize sperm, and resist implatation onto the uterine wall. Mirena and Paragard work uniquely to prevent pregnancy.
ParaGard can be used as an emergency contraceptive device as the copper fillament in Paragard works immediately to prevent implantation by changing the lining of the uterus. Because of this, even if a sperm does fertilize the egg, the embryo cannot attach itself to the endometrium (uterine lining).
Mirena releases small amounts of the synthetic progesterone suppliment named Levonorgestrel which thickens cervical mucus thereby making it difficult for the sperm to enter the uterus. Also, like the ParaGard, it prevents implantation by changing the uterine lining.
