Many factors influence the growth of a child, including: parental height, nutrition, exercise and significant or chronic illnesses. The first step to understanding the child's growth is to ensure all measurements are as consistent and accurate as possible.
Try to always use the same scale (or at least note which scale was used, to help understand discrepancies). Weigh your child in the same clothing or while undressed. If weighing an infant, try to weigh him or her without a diaper on. If this isn't an option, ensure there is a new (clean and dry) diaper on. Weight fluctuates significantly throughout the day and in relation to meals and bladder and bowel movements. To minimize the effect of these, try to measure weight on an empty stomach, bladder and bowels. Measuring at the same time of day (first thing in the morning, or just prior to bath time) can help minimize some of these variations.
When measuring height, it is sometimes difficult to obtain accurate measurements.
Measuring Head Circumference:
When measuring head circumference, use a cloth or paper measuring tape, and place it around their head at or slightly above the level of the eyebrows. Move the measuring tape up and down to try and find the location with the largest/longest circumference around their head. Note the measurement on the tape where it meets up with the line for zero at the beginning of the tape.
Once accuracy and measurement variability is accounted for: If your child's growth seems to be falling off, not following a growth curve, it may be important to follow-up with a certified child health professional (physician, pediatrician, dietitian, nurse practitioner, etc) to understand why this is happening. If you notice a trend of decreasing growth, or multiple curves being crossed over multiple measurements, it is very important that you do see your child's health professional to look into the possible reasons for this. This is important as many of the causes for this are able to be modified before the child's cognitive development or final stature are affected.