That's true... but I imagine if they extended it that far, reproduction rights of the child would be included in the license. Unlike corn, I can't imagine many parents would agree to sterilize their children just to include some synthetic DNA sequence. Even if the parents were very desperate (because of some genetic problem), they would still want their child to be able to reproduce.

assuming the parents understand the contract in which they are entering.

They wouldn't need to sterilize the children, nor would the corporation be interested in that. Just think of the recurring revenue!