Re: new to fleece
Microfleece will let moisture through with pressure. It's a great inner layer for a diaper, or the pants are great over the top of an otherwise moisture proof diaper, say for nightime backup protection. But it doesn't make a good standalone cover.
Thicker fleece, such as blizzard fleece, anti-pill, windpro, etc, will give you MUCH more waterproof protection.