svt and pregnat

my daughter was born with svt and is going to have a baby how will this effect her and the baby

[Cleveland Clinic]

there is a higher likelihood that the baby will have SVT, but the mode of transmission isn't classically mandelian, meaning that the risk is not 50%.  It is much smaller.  I would not be very concerned about that at all.  If she develops more SVT during her pregnancy (which is common), there are meds that can treat it effectively.  There really isn't any serious to worry about.