Family history?

hi everyone! just found out I am pregnant today about my first

IVF

cycle! had a question about family history on my husbands side. his sister has 4 children. the oldest is severely intellectual disabled . she’s almost 20, nonverbal and was born with a heart condition. no one knows the cause, his sister says it was a birth accident from the umbilical cord being wrapped around her neck, but no one knows for sure. we don’t t have a relationship with his sister or the neice to get further information. my husband and I already have a healthy 3 year old but I think I am more worried about this now with my second because it took us longer to get pregnant and had more time to think/worry. we did PGS testing on this embryo. I also got the carrier testing done before becoming pregnant. I spoke to doctors and a genetic counselor who really said can’t tell me exactly what the reoccurrence risk would be since it’s unknown but thinks it’s low risk. so my question is- am I worrying for no reason? just want to hear from other mommas!!!