Quoting Elijah C's Mommy!:" What size did/does your 4 month old wear? My 4 month old wears size 3. We switched to size 3 when he was a few days before 4 months old. He's 15lbs."
Quoting NICKEL☮POLIS:" I think DD was into 2s by then. She is 9 months now and in 3s. Can wear 4s but they are a little big"
Quoting ♥ logan's mommy:" yep, my son's 4mo (5mo on 10/21) and he's been in 3's for a while. He started getting red around the ... [snip!] ... area from them being too tight. So around 3.5mo we switched. Already thinking he needs to be in a 4 lol. He's 16lbs btw "