3 year old boy has childhood apraxia of speech diagnosed by speech pathologist.how can i know if the vacuum at birth caused it.no one in family has it?

Not possible: Do not think it is possible to be able to attribute this to the vacuum, it could be a different reason

True Developmental: Apraxia (DA) is usually genetic or of unknown cause. MRI's rarely show congenital malformation or damage in brain regions that control speech & language. A team of developmental/behavioral pediatrician, pediatric (neuro)psychologist, SLT & OT should differentiate DA from Autistic Spectrum Disorder & Global Developmental Disorder, singly or together & isolated Expressive Language Disorder for you

Short circuiting: Think of speech apraxia as a wiring mixup (short circuit) triggered by unknown factors.Vacuum extraction is similar to the pressures on the pliable head structures in a natural birth. It doesn't make the wiring change inside. It also doesn't occur as an isolated feature of kids who suffer known head trauma after birth.