My baby girl was 9lb 14oz and was in 0000 for two weeks, the only issue was her feet were too big really. I hate the oversized baggy look on my babies so I was happy to have 4-5 0000 suits just to cover those first few weeks. One thing to remember is that Bonds sizing is generally a size smaller, so if you're buying wondersuits a 000 is closer to any other branded 0000