Where do IUD strings go if they get lost?

Some men feel them during intercourse, that is one way - the other is to insert your finger and use a sweeping motion to feel for the string. If you can't feel them, bare down (as if you were having a bowel movement).

Never try pulling on them, you could end up with a perforated cervix or uterus.

If all else fails go in to see your MD or midwife, they can tell you very quickly if the IUD is in place, it is rare but the IUD occasionally may slip out un-noticed, so if the strings are not where you remember feeling them, see your doctor.