IUD or Intrauterine Device is a small, plastic, T-shaped contraceptive.
It is placed in the uterus to prevent pregnancy.
IUD comes in two types – those containing copper, called Cu IUD, and those containing hormone systems, called Hormonal IUS. The methods that both systems use are slightly different but essentially both prevent pregnancy by making it difficult for the sperm to survive inside the uterus or to reach the egg in the fallopian tube.
Copper IUD : The copper IUD works by obstructing the movement of the sperm as it moves towards the egg. This prevents fertilization. It also affects the lining of the uterus, making it difficult for the fertilized egg to get implanted on the wall of the uterus. This may not be suitable for women who are allergic to copper.
Hormone based IUD : The hormone based IUD, which is also known as IUS (Intrauterine System), releases a small amount of Levonorgestrel, which is a progestin. This reduces the frequency of ovulation and also changes the cervical mucous so that the passage of the sperm through the cervix is reduced/ impeded.
In both cases, with the copper as well as hormone system, the presence of an irritant in the uterus causes the body to release leukocytes and prostaglandins, which are spermicidal as well as harmful for the egg.