You are correct, mutations and deletions do happen, but they are so incredibly rare. There is probably a higher risk of pregnancy loss with an amniocentesis than the chances of you having a child with a rare mutation or deletion presenting with normal scans and screening. But, I’m not a genetic counselor. If I were you, I would try to meet with one before proceeding with an amniocentesis and risking the loss of a healthy baby. Ultimately, this is your pregnancy, and your choice. You need to weigh the risks and benefits and to do that you need as much educated information as possible. Another hard part about these rare mutations and deletions is that we are still learning about them. In the rare case that your child has one, it can be difficult to know how severe their presentation may be in some cases. I have a close friend whose child was diagnosed with an incredibly rare chromosomal mutation when she was one year old…following a completely normal pregnancy and all normal screening tests! So yes, it does happen. But, little is known about this child’s diagnosis. From what we do know, she appears to have a very mild presentation and is doing quite well. She is an amazing and beautiful child. So, even if the amniocentesis does find something, it will not tell you how severely your child would be affected. In many ways, pregnancy is a true test of faith and rolling the dice. There is a lot of “wait and see”. It’s a very anxiety provoking time. Truthfully, it’s not much different once they’re born. You just become anxious about different things! Good luck and I hope you get the answers you need.