We know that Adam and Eve had Cain and Abel and their 600 (I forgot the exact number) after Heaven was taken from them for consuming the fruit. But if hypothetically, if they hadn't sinned, would they give birth to new humans in Eden?
God says before "the fall" that He blessed man to be "fruitful, and multiply, and replenish the earth".
However from what I understand Adam and Eve didn't know what nakedness is, they seem to be so innocent that they wouldn't even know how to "multiply" before eating the fruit, and indeed they didn't had babies in Eden. It seems to me that initially God didn't want billions of humans, just two.
Some even propose the theory that the fruit is a metaphor, a symbol for the sexual pleasure of Adam and Eve. I know some modern literature (not in English, not religious related) that uses the wording "girls that didn't yet tasted the sweetness of the fruit of sin" to describe a virgin woman.
Maybe before the fall, God designed mammals with a non-sexual multiplication, similar to the idea that God designed all creatures to eat plants, but after the fall he permitted meat-eating in humans and animals.