It is indeed possible to get pregnant with an intrauterine device (IUD) in place, because IUDs are not 100% effective at preventing pregnancy. Around one in 100 women can get pregnant with an IUD, according to clinical trials conducted with IUDs, and the outcome of the pregnancy varies, depending on the woman, the IUD, and the situation. Due to the fact that pregnancy is a potential risk with an IUD in place, it is important for women to keep track of changes in their bodies while using the IUD, so that a pregnancy can be identified in the early stages.

An intrauterine device prevents pregnancy either by preventing sperm from reaching the egg, or by altering the uterine lining so that fertilized eggs cannot implant and develop into fetuses, making it difficult to get pregnant with an IUD. Copper IUDs accomplish this by secreting copper into the uterus, while hormonal IUDs release progesterone. IUDs are actually the most effective way to prevent pregnancy after abstinence, with hormonal birth control failing in one to two percent of cases, with a failure rate which is even higher when the pill is not used properly.

The advantage of an IUD is that it is very difficult to use an IUD improperly, in contrast with other forms of birth control which may need to be taken every day or attended to prior to each sexual encounter. As long as a woman checks her IUD strings regularly, the IUD is considered to be in place and working. However, it is still possible to get pregnant with an IUD, because sperm are nothing if not determined, as also is human life in general. Women with unusually large or small uteri may also get pregnant with an IUD in larger numbers than women with uteri which fit within the range of those tested during development of the IUD.

If a woman becomes pregnant while using an IUD, most doctors recommend that the IUD be removed so that it does not interfere with the pregnancy. In some cases, the removal may pose the risk of a miscarriage, in which case the IUD will be left in place. The IUD will not usually hurt the baby, but it can cause developmental abnormalities. In other instances, a woman may opt for an abortion because she does not feel ready to have a child. The pregnancy may also miscarry naturally, with the risk of miscarriage being increased if the IUD is left in place.

One big risk of getting pregnant with an IUD is that use of an IUD increases the risk of an ectopic pregnancy, a pregnancy which takes place outside the uterus. This kind of pregnancy is extremely dangerous, and it requires immediate medical attention. Women who think that they have become pregnant while using an IUD should go to a doctor to confirm the position and status of the pregnancy, no matter what they ultimately decide to do about it. Using condoms can also reduce the likelihood that a woman will get pregnant with an IUD.