What are the chances of pregnancy after loop insertion?

Q: I am 31 years old. I have a child after which I had a loop inserted to prevent pregnancy. I was supposed to have my periods this month but I am yet to get it. Is there any possibility of pregnancy even after the insertion of a loop. is it right that the loop should be changed once in 3 years?

A:An intra-uterine device (IUD) causes cervical mucus to be thicker in consistency, thereby altering sperm migration. Utero-tubal fluid and motility changes inhibit sperm migration. IUDs also result in endometrial suppression. Medicated ones also act by releasing the hormone. The failure rate (depending on the type) ranges from 2% to 0.1%. Again, depending on the type used, the IUD must be replaced every year to every decade.