DD was 2.9kg and in 0000's for a good few weeks. She fit 00000 for a while but we didn't have many so just wore 0000's which were kind of swimming on her at first haha. She was full term, just a little bub!

It is hard to know what you will be needing!
My DD was 2.9kg also and full term! She was in 00000's for about 2 weeks and then 0000 for a couple of months, she was short but with long arms so we had to go up a size for the arm length to 000 but still in 0000 pants for quiet a while.