DescentBB

Simple: killing 'em when you can't see 'em makes it a lot easier. If you wait till they are born, you also enter into the realm of infanticide.

Remember, a magic process occurs when a baby is born, it ceases to be tissue and becomes a being with its own rights. Best to snuff them out before that occurs.

Anyway, "too many humans on the planet" is only a good justification for suicide, genocide, and homocide. The easiest and quickest option is the first.

If we could find the source of that magic dust that transforms tissue into humans and prevent it from being sprinkled upon the newly born, science could alleviate food shortages as well. Only worry there is most people prefer the white meat.