Some degree yes, but mostly it's based on gestation and the reality that certain development is required for life in any measurable way to be completed, the ability to life outside of the host (Mom) is also a factor.
After a certain point of development (time) being used an overall factor legally. But there are margins even for time after that where there still not enough development to assign any real expectations.
The law already exist that the chance of that kind of development is extremely low.