Took DS to the clinic to be weighed this afternoon, and at 18 days old he weighs the same as at birth. Should I be worried by this? He seems to be feeding very well (I'm feeding on demand, and he's feeding loads during the day, including cluster feeding for three or four hours in the evening, and then waking up a couple of times in the night) and has plenty of wet and dirty nappies, but the HV looked worried and insists we take him back next week to be checked. Help - has anyone else had this and subsequently found that everything was OK?