That would be quite interesting. And it would be cool if the made the gestation time more scientifically correct.
An example is that an Elephant's true gestation period is around two years, not about 2 months.
Another cool idea would be that if an animal is pregnant, and it doesnt have enough food, or water or its basic and advanced needs aren't being met, the foetus will die, showing a message saying something like:
"Due to lack of food, Bengal Tiger 1's foetus has died"
Just an example.