Animal shelters around the nation are full of pets that need homes, and always have more than they can find homes for. That means pets are dying unwanted, or being put to sleep because they can't afford to keep them. How can anyone, knowing that, justify breeding a pet and making more?
I've seen both dogs and cats giving birth, and I know the whole thing about it being a beautiful sight. Sure, it's profound and moving, let's just grant that. So? Watch a bloody video already. You don't put a creature into a life that's doomed to be miserable and unwanted and maybe short just so you can have a profound and moving moment.
But you'll make sure your pet's pups or kittens get good homes, so that's not what you're doing, right? Wrong. Maybe that tiny kitten in your cupped hands will go to someone who wouldn't have taken a kitten otherwise, sure. But odds are good that at least some of those puppies will prevent some other puppies from getting adopted. You just can't add to an overflowing tank and not create overflow by doing it.
So get your pet fixed (more accurately, broken). It's good for your pet and it's good for everyone. And when it's time for a new one, get one that needs a home.