Hi there, I am a married female and my husband had vasectomy about 3 years ago. Since then we were enjoying sex as normal. But I am very much concerned about chances of pregnancy, as we used to have unprotected sex, since then. I feel his ejaculate inside me, which makes me tense about getting pregnant. Is there any chance in males that vasectomy can fail? I heard that, during the process, some tubes which carry sperms are cut and tied. Is there a chance that the knot get untied and start releasing sperm to urethra, making him fertile? Some kick, knock or beating can release the knot, I think. I am very much concerned about it and it makes me tensed while having sex. I heard that vasectomy is very effective but I am not so sure about that. Please help me.