Best of luck and try not to worry! Very similar happened to my aunty in law with her youngest daughter, though in her case the placenta just seemed to stop working properly. She had a c-section at 36 weeks though her daughter was only about 3lb and very tiny. They kept her in hospital for a couple of weeks until she got to just under 5lb then they let her come home. She was fine just gained weight very slowly for the first year and could still fit in 0-3 when she was 12 months, after that though she gained weight and height a bit too well which is apparently quite common. Things have settled down now though and she is just a little bit taller and heavier than others her age and has suffered no long term health effects from being born so small for dates xx