This link contains patient information from QLD Department of Health about Weight Gain and Healthy Eating in Pregnancy.
(Note that if you are not in QLD you may not be able to access the telephone advice line number mentioned in this information).
If you have a single pregnancy (ie. not twins or triplets) you should aim to gain the following amount throughout pregnancy:
Pre-pregnancy BMI less than 18.5 12.5 – 18 kg;
Pre-pregnancy BMI 18.5 – 24.9 11.5 – 16 kg;
Pre-pregnancy BMI 25 – 29.9 7 – 11.5 kg;
Pre-pregnancy BMI more than 30 5 – 9 kg.
Weight Gain & Healthy Eating in Pregnancy (QLD Health)