Hi Kanchan. Weight of the baby has to double the birth weight by the 6th month for a healthy weight gain. According to your parameters baby looks fine. Sometimes babies are over active because of which they do not have the chubby fat on them. If your baby is gaining weight, eating well, being active, nothing to worry. Thin or fat is just a way of judging for no reason. It doesn't imply anything medically. However if this bothers you keep a check on her weight gain and her feeding routines