There are several ways that Paragard prevents a pregnancy from occurring. First, it makes it difficult for the sperm to reach the egg. It also makes changes to the eggs themselves so that it is harder for them to become fertilized.
In addition to this, the IUD can make it harder for the egg to attach to the uterine lining because it affects the health of the lining by making it thinner. When the lining is thinner, the embryo will have a harder time attaching, even if it does become fertilized.
Because of these changes, it is nearly impossible that you will become pregnant while the Paragard IUD is in place. However, it is only 99% effective and a few women do become pregnant with the device. If you do find yourself pregnant, you will need to have the device removed as soon as possible. If left in place, there could be pregnancy complications or the pregnancy could result in a miscarriage.
If you are looking to become pregnant, your doctor will be able to remove the device at any time. However, keep in mind that the changes to your body could take a while before they revert back to normal. Taking the device out several months before you are ready to conceive is usually the best option.