Postural Development In Very Low Birth Weight & Normal Birth Weight Infants

A baby's birth weight can make a significant difference in the way she develops. Depending on if there are any neurological or physical complications, the baby may initially appear delayed but will often catch up by the age of two. Babies born with a very low birth weight, or between 3.3 to 4.4 pounds, are at risk for numerous medical complications and motor delays. A normal birth weight infant is between 6 lbs, 2 oz. and 9 lbs, 2 oz.

The First Month

Babies are normally born with physiological flexion, meaning that the spine is curved like a C and the legs and arms are held closer to the body. This is based on the position the baby maintained in the womb. Infants who are very tiny have more space in the womb and are not restricted by the uterus to this position of flexion. Therefore, they may show more extension at birth than a normal birth baby.

Postural Development in the First Four Months

In typical development, an infant begins lifting his head while lying on his tummy by the time he is two months old. This may be delayed in the infant with VLBW as the baby's head size is often much larger than his body size, and therefore heavier to lift. The normally growing and developing infant can then extend his trunk against gravity and prop himself on his forearms to look around. When lying on his back, the three to four month old has the postural control to bring his hands together at midline. The preterm VLBW baby may be delayed or continue to show more primitive movements; however, evidence suggests that the delay is related more to prematurity than birth weight.

Postural Development from Five to Nine Months

The typically developing baby can roll over at five months and sits independently by six months. There is a balance of strength between flexors and extensors; the baby can bring her feet to her mouth and can reach for objects while on her tummy. Preterm babies may not have this same balance in the muscles and may show less rotational patterns for rolling and crawling. A recent study in the journal Acta Paediatrica found that 50 percent of VLBW infants were sitting by seven months when age was corrected for prematurity, but overall were more delayed than the NBW infants.

Postural Development from Nine to Twelve Months

Babies have the postural control to crawl by eight to nine months, and to walk by around twelve months. Fine motor skills also develop; the baby can stabilize his posture in sitting to reach and grasp with his hands. Babies with VLBW are more slightly more delayed in walking, but should be able to walk by thirteen months corrected age.

Complications in the Research

Most babies who are VLBW are in the category of preterm, or born prior to 37 weeks; however, research does not always separate the effects of prematurity from the effects of birth weight. Datar and Jacknowitz compared VLBW infants to moderately low birth weight infants, and there were statistically significant differences in their motor development at the age of nine months. However by age two, the VLBW infants appeared to catch up.