Can a ultrasound at 5months along be incorrect?

Answer 1

It's possible that the technician doing the ultrasound read it wrong. The baby may have been in a position that made it harder to determine its sex. If it's a question of whether there's something wrong with the baby, then you need to consult with the doctor and have another test performed.

Answer 2

Depends. incorrect for what? Either way, I'm not a doctor for I'm assuming that for most things, nothing is for certain until the baby is actually born.