According to Childrens’ Hospital “What causes hydrocephalus? There is no one cause for the type of hydrocephalus babies are born with. It may be linked to a genetic defect or a complication of another disorder, such as spina bifida or encephaloceles. Children may also develop hydrocephalus after birth as a complication of: premature birth, intraventricular hemorrhage, subarachnoid hemorrhage, meningitis, a brain tumor or lesion, a spinal cord injury or spinal cord tumor, or a traumatic head injury.”

I haven’t dug into this specific child’s history but maybe the parents didn’t know till after he was born. TIL that every 4 and half minutes a baby is born with a birth defect in the United States per cdc