Hi, our baby has lost a lot of weight (she is 2 weeks old and lost 20% of birth weight though is slowly gaining weight now) and on advice of pediatrician we are having to top up her breast milk with expressed breast milk and formule when I can;t express enough- having not prepared for this I am confused re sterilisation. We have been given an avent steam steriliser - how long after using it does the stuff in it remain sterile? Also I have to screw the bottles togetehr by hand - doesn't this make them unsterile or if I don't touch inside of bottle or the teat is it okay? And what about making up botles to take out the house - how long are they okay for when I;ve done this? tbh I don't understand how to use bottles at all really - I hadn't even looked it up so sure was I we would exclusively breastfeed.