More About "Back to Sleep": The Neglected "Tummy Time" Part

Yesterday I posted some comments on the complex causes of Sudden Infant Death Syndrome (SIDS) (http://childmyths.blogspot.com/2013/12/sids-sleeping-position-and-single.html). I pointed out that there are many factors that increase the risk of SIDS--  that supine sleeping is not the only one, even though it has received the greatest emphasis by far. I ended that post by referring to adverse events associated with supine sleeping.

One of these unwanted side effects, deformational plagiocephaly, I have written about at http://childmyths.blogspot.com/2014/05/flattened-skulls-helmets-not-much-use.html. Lying in the same position for long periods can flatten an infant’s still-soft skull, which gradually hardens into an asymmetrical shape. Once flattening has begun, the baby’s head naturally turns to place the flattened area down, increasing the extent of flattening. But although the resulting asymmetry can have an effect on ear positions, it does not damage the brain or otherwise cause problems. (As anthropologists have pointed out, there have been many cultures that intentionally bound or flattened baby’s heads to get an appearance that they considered highly attractive.) Still, most parents today would rather their babies did not have flattened or asymmetrical heads, so paying attention to babies’ head positions and varying them is probably a good idea when babies sleep supine.

A more complicated side effect of supine sleeping as currently practiced by many parents is that some early events in motor development are delayed (see Pin, T., Eldridge, B., & Galea,M.P. (2007). “A review of the effects of sleep position, play position, and  equipment use on motor development in infants.” Developmental Medicine & Child Neurology, 11, 856-867.) The review by Pin et al indicated that motor delays are due not simply to supine sleeping in itself, but result from the lack of experience of the prone position during waking time. Here are the conclusions of this review paper: “In healthy infants born at term, those who spent time in prone when awake achieved developmental milestones significantly earlier than those who did not or who spent limited time in prone when awake in the first 6 months of life… Those infants who slept in supine attained developmental milestones significantly slower than the norm… before 6months of age…. most of these healthy infants born at term walked independently or developed within normal age limits. … Low-risk preterm infants who slept in supine attained head control… and rolling between supine and side and bringing hands to midline significantly slower than infants sleeping in prone or non-supine positions. All these preterm born infants walked independently within normal age limits”  (p.865).

Why would experiences with supine or prone positions make a difference to motor development? It’s easy to think that motor development just “automatically” progresses from the top to the bottom of the body, just as we see physical growth proceed in the cephalocaudal direction. But motor development involves both maturation of the nervous system and practice which leads to muscle development. Full-term newborn babies lie in a flexed “fetal” position and need both maturation and appropriate exercise to be able to extend the body. When babies are in the prone position, they can be seen working on this from the first days of life, lifting the head awkwardly and turning it from one side to the other. With arms under them, they soon become able to lift the head briefly to look around. Within a few months they can extend the arms enough to get the shoulders up, then chest up with fully-extended arms. These achievements depend on strengthening the muscles of the neck and shoulders by exercise. Babies who spend most of their time in the supine position will eventually develop muscles and motor skills, but the supine does not provide the same opportunities and challenges for mastery of arm extension as prone does, and it forces the baby to work against the pull of gravity.

Is this phenomenon of motor delays a problem? In one sense, no, it is not. The evidence is that these babies walk and show other motor abilities within a normal age range. This is not very surprising, given evidence about other cultures that limit babies’ movement capacities. Margaret Mead reported in the 1930s that Balinese babies were never permitted to crawl, this being considered “animal-like” and incongruent with the babies’ recent arrival from the divine realms. Yet, the babies walked independently within a normal age range. Similarly, Geoffrey Gorer described the use of swaddling for babies up to a year of age in Russia, but found that the babies walked independently within a normal age range even though they had had very limited experiences of independent movement.

In another sense, though, motor delays may be a problem. A common and effective way of assessing early development involves comparing an infant’s motor skills to norms developed by observing large numbers of babies. But the norms we have now were developed at a time when almost all babies slept prone, so they do not necessarily give a good comparison for babies who sleep supine. These “outmoded” norms make it difficult to know whether a young baby’s development is progressing in a typical way. This may be especially important now that there are reports of slow motor development as a predictor of later communication problems in infants at risk for autism (see Bhat, A.N., Galloway, J.C., & Landa,R.J. [2012]. “Relation between early motor delay and later communication delay in infants at risk for autism.” Infant Behavior & Development, 35, 838-846). The diagnosis of genuine motor delays may be important in more ways than one.

Is there anything that parents can do to encourage good motor development in their supine-sleeping  babies? The first step would be to use “tummy time” regularly and to work with reluctant babies to tolerate and later enjoy the prone position. “Tummy time” may be awkward at first, but the baby’s motivation for mastery of the environment will soon help move the process forward, especially if parents have been given good information about what to do.

  

Is there evidence that “tummy time” or other techniques do any good for motor development? There has been an experimental study showing the effects of a program to encourage motor development (Lobo,M.A., & Galloway, J.C. [2012]. “Enhanced handling and positioning in early infancy advances development throughout the first year.” Child Development, 83, 1290-1302). These authors noted that the prone position is challenging to young infants and that most caregivers tend to avoid it. They taught caregivers in the experimental group to do the following for 15 minutes each day, beginning when the infants were two months old: “placing them on the floor or [on the] caregiver while encouraging them to push up to lift their head.. pulling them up [by the arms] and lowering them down while assisting them to keep the head in line with their body…supporting them in sitting and standing while encouraging them to weight bear and to reorient their body upright with respect to gravity, and… moving their hands to midline for play to encourage a shift from lateral to more midline arm placement” (p. 1292). Caregivers in the control group put their babies in the supine position and played face-to-face with them for 15 minutes a day. The caregivers in both groups continued their activities for three weeks.

The  babies in the experimental group were earlier than the control babies in their achievement of reaching for an object at the midline, transferring objects from one hand to the other, creeping on hands and knees, walking with support, and walking independently. This intervention apparently counteracted the motor delays associated with supine sleeping.

I think an important point about the success of the handling and positioning intervention is that caregivers were carefully taught what to do with the babies. They were provided with an illustrated manual and a diary to record their activities with the babies. In addition, activities were suggested other than simple prone positioning--  the prone position being especially feared by parents who know that SIDS risk is much higher when babies who are accustomed to supine sleep are placed in prone. The usual casual admonition to ”do tummy time” does not convey much information to caregivers, and new parents who delay prone positioning until their baby is three or four months old will probably find that the baby objects strongly to an unaccustomed position, a situation that further discourages anything but supine positioning.

Perhaps an appropriate change in the “back-to-sleep” mantra would be “Back to Sleep; Tummy to Be Played With”.  Young babies don’t exactly play by themselves, but as the song says they can remind us how to play, and our mutual enjoyment can encourage good motor development.