I agree with what the other ladies have said. My first baby was 9lbs and I had a crappy labour (strike that - very crappy!) Anyway, I had read somewhere that babies just tend to get bigger the more you have. Every OB appointment I had after about 30 weeks, they kept telling me, "Woahhh.... this is another big baby, or yes it is definately bigger than normal" Well, just like you , I was absaloutely freaked out thinking, Oh god, I cant possibly do a baby bigger than 9lbs!
Anyway, my daughter was born a perfectly healthy 7lbs7. And only 49cm. She was perfect. So do not always go with what the OB tells you. They are only guessing after all - you wont know for sure until your little one is born!
Good luck with everything!