Anyone know of or have a child with an extra X chromosome? When doing further testing for Down syndrome (just a blood test drawn from me) we found out that my baby girl was negative for Down syndrome, trisomy 13 & 18. 😊 Thank God for that! But they did discover that she has an extra X chromosome. They say it's not as serious and they don't know as much as they would like about it bc most people that have don't ever find out unless they have Fertility problems later. It's said that it can cause your child to need more help with learning or to be a little taller then the "average" woman. I'm just curious if anyone has this or knows anyone that does and if they can tell me if it affected them in anyway.