Though IUDs (copper as well as progesterone releasing) are very effective means of birth control, they have a failure rate of 1 to 2%.
When a pregnancy does occur with an IUD in place the following are possible complications that could occur:
- Ectopic Pregnancies have a higher chance of occurring in the presence of an IUD rather than without it.
- There is an increased change of a pregnancy ending in miscarriage when there is an IUD in place. If the device is removed as soon as the pregnancy is known, that risk does come down, but it remains higher than in other cases.
- The chances of an infection with an IUD in place are also higher. This infection can in turn cause a miscarriage or later pregnancy loss.
- If a pregnancy occurs while and IUD is still in place and the device is not removed as soon as possible, this also raises the risk of having a preterm child. This can in turn cause certain irreversible and permanent problems for the child.
These possibilities however are not common, since the IUD is a safe, effective and reliable device for birth control in the main.