My tip is to buy things (Bonds singlets, suities etc) from Big W or Kmart in sizes 0000 and 000. Then when bub is born and you find that you may not need the 0000, just return them. Keep the receipt with them and don't cut tags and there is generally no time limit on returns. That's what I did. I also bought a mix of boy and girl stuff and then returned the boy stuff as we have DD. Don't buy far ahead though- we have gone from 0000 to 000 to 00 and now buying 0 in 4 months. And people give you heaps!