I weighed 97kg when I fell pregnant with DS. I was 108kg when he was born and he weighed 10lb 13oz or 4.9kg. Doctors say that its because of my weight. But I think it is due to how much nutrients etc the baby gets from you while you are pregnant, and genetics would also play a part. But who really knows. I am a firm believer that you grow a baby to size that your body can handle and birth. Obviously there are exceptions to the rule.