Modern intrauterine devices (IUDs) have come a long way since the 1980s, when they fell out of favor. Today's IUDs are safer and more effective than their predecessors. Even so, there are still some complications you may have to deal with. One of the main complications with IUDs is expulsion. In a small number of women, an IUD can be spontaneously expelled from the vagina or dislodged from its proper position. This is most common in women who have never had vaginal childbirth, and when the IUD was inserted soon after vaginal childbirth. It's recommended that you check for the string that hangs down from your IUD at least once a month (usually after your period) to make sure to make sure there aren't positioning problems. If the string is shorter, longer or you can't find it with your fingers, it's possible that your IUD has been displaced. When an IUD is not in its proper position, its effectiveness is compromised. Until you can be examined by your doctor, it's wise to use a back-up birth control method such as condoms to prevent pregnancy.