I'm no expert, but I seem to remember this coming up in one of my paralegal classes and the argument was that a child is a blessing / provides it's own rewards or something to that effect and therefore there are no grounds for a lawsuit based on cost of raising the child when an unwanted child is born.
The exception for medical costs when the child has medical problems is because that presents a hardship and I suppose the blessing / rewards are not the same.
It was a point of major discussion within the class for the majority of the morning session. I don't remember exactly, but it may have also had something to due with having to pay child support.
Adoption probably would have been an option for this woman. I wonder why she didn't do that.