i used a HAB (hug-a-bub) which was great. My daughter was 4lb 15oz and she fit fine into it from day dot. She's now 16 months old and 9kg, and we still used it often. We're lookin at upgrading to an ego, when finances allow. But either a sling or a HAB is great. And if u take great care of it, you can chuck it on ebay or something when you're finished with it

HTH, good luck xx