Bulky Weight Longies
This pattern was designed to be used as a nighttime diaper cover. The thickness of the wool makes it more waterproof than worsted weight. If you wanted to make it even more water tight, try knitting them in garter stitch.
A huge incentive this pattern offers is that it is a quick knit. If your little one sizes up before you are ready, these longies knit up in almost no time.