IUDs primarily work by preventing fertilization, but fertility has been shown to return to previous levels quickly after removal of the device. Fertility is restored immediately after removal of the device; irrespective of whether the IUD was used for a few months or for many years. Failure rates are about 0.8% with copper devices and 0.2% with hormonal (levonorgestrel) devices in the first year of use.
A perforated IUD with copper has been reported as a rare cause of secondary infertility, i.e. the inability to become pregnant or to carry a baby to term after previously giving birth to a baby. Hormonal devices perforated to peritoneum can cause suppression of ovulation and resulting infertility. Inasmuch as the ovulation is the release of egg from the ovaries, there is no egg available to fertilization if the ovulation is suppressed. Removal of device can help in restoration of fertility.