Height, Weight and Head circumference: While all babies may grow at a different rate, the following indicates the average for boys and girls. There is no cause for alarm just because the timing of a child's development is slightly different. Average weight gain is 0.57 kilograms each month and by 6 months, a baby must have doubled his/her birth weight. Average growth in height is ½ to 1 inch each month and head circumference, about ½ inch each month. Plese also refer to the following link https://www.webindia123.com/health/child/baby/milestones/foursix.htm