Depends how you interpret it. If you say a new universe is created with every quantum decision, then you could argue that(though I've always treated conservation laws as being descriptive, not proscriptive - there's no operation which changes the net amount of mass-energy, so it's conserved, but that's not a philosophical requirement). But the treatment of many-worlds I see more commonly is that there's already an infinite number of worlds, and it's merely a newly-distinct world that is created with a quantum decision.