That we aren't that different is why there's an ethical problem.

Unless the prenatal environment for a human is the same as say, for a gorilla, so that a gorilla could be a surrogate parent for a human, I wouldn't expect the animal testing to be an acceptable way to know how a human baby would turn out.

I also imagine it's pretty difficult to do mental health screening on a gorilla, let alone extrapolate to whether a human baby would turn out physically okay but mentally not so great.

What if the problems aren't clear until the child is born? Or a toddler, or a teen? There's still a lot we don't understand about prenatal environment and how it contributes to the attributes someone has as an adult.

One of the best arguments for allowing abortion is that we do not force anyone to risk their integrity and life for another person, which is what pregnancy is. This argument won't work anymore.