Dee although I can't comment on the FBC placing - I was the same as you...around 75 kg and just under 5ft 3 before pregnant. I put on around 18 kg before i got to term. I don't think you should be trying to lose weight - but try as hard as you can to minimise any gain. from what i understand it is a BAD idea to diet during pregnancy - as what you are missing out on baby is too - but a healthy eating plan should get you through.
oh and I am back down to pre-preg weight and i do not consider myself obese - just cuddly!