I am worried as I don't appear to have put on any weight in the first 13 weeks. Why?
Many women do not put on weight at this stage because the pregnancy uses the maternal reserves to thrive, and at this time the baby actually needs few calories to grow. Often because of nausea and morning sickness, women can even loose weight at this stage. Do not worry; true weight gain usually occurs in the latter 2/3rds of pregnancy.