Matilda's been up & down the last 4 months. When she turned 12 months she was 9.7kg, and last week she was 10.6kg. So in 5 months she's gone up to 10.5kg and back down to 10kg and up again. I think it happens as they go through growth spurts & then settle down again. I asked the ECHN last time I was in & she said Matilda was still going well on the chart, and looked good so not to worry any more. but like Cailin said, if it is a concern definately chat with your Dr about it.