Healthy infant growth is not decided only by weight. Motor skills, length, weight, mid upper arm circumference, triceps and subscapular skin fold thicknesses are all factored in when deciding if a child is growing and developing at an adequate pace.
A baby's weight varies for every individual. A baby gains 5 oz. to 7 oz. a week. According to the experts at the Mayo Clinic, a baby's weight at 20 weeks should be approximately double the baby's birth weight. Do not worry if your child experiences pauses in growth; according to the Mayo Clinic experts, this is normal. Concern is not necessary unless your baby does not grow between baby wellness examinations.
A baby's height or length is also a key factor in deciding whether a baby is developing at a normal pace. When a baby reaches 20 weeks, he should be more than double his length at birth.
A child of 20 weeks should have certain motor skills. A child of 20 weeks should be able to lift her head up and look from side to side. Infants should be able to roll over from stomach to back, and from her back to her stomach. Some children can sit upright in a high chair by five months of age. Infants also have some speech milestones that should be met by 20 weeks. This includes smiling when a parent appears, smiling when spoken to, and making soft cooing sounds.
If one or two of these milestones are not reached by 20 weeks, it is not cause to worry. Every baby grows at a different pace. If a child is not at double her birth weight and height it may be a sign of undernourishment. If a child does not reach all or most of her developmental goals, consult a pediatrician to find out if her central nervous system is developing correctly.