
In my experience, I am afraid, the only answer is 'wait and see'. I have had tiny ones in litters who carried on being small all their lives, and others who cought up at about 6 - 8 weeks. A couple of instances: Titch was born at about half the weight of his siblings, had to be hand supplemented, it was touch an go if he would live for at least 2 weeks, wight gain was so small but it was consistent. At 6 weeks he was still slightly less than half the wieght of siblings, but very lively - and a lot less coat. At 6 months we was proportionatly a half size american cocker, and the coat was coming. At 1 year he was small for a male, but not a "miniature" by any means - more the size of a bitch, but very study and so much coat it was a nightmare. On the other hand, Bianca was one of a litter of 6 girls, and she and 1 sister were exactly half the wieght of the rest. However, they gained perfectly acceptable amounts of eight every day, and all development stages were reached as expected (doubled weight at 10 days, eyes opened at 12 days etc). At 4 weeks they were still exactly half the weight of the rest, but quite perfect, and at 6 weeks put on a growth sprut, so that at 8 weeks they were petite but not too tiny. At adulthood Bianca is a beautiful, excellent specimen of an American cocker, and would probably have made up if she had been temperamently suited to showing ;)
bye
Gwen