Dear all:

Having had epidemiology up the wazoo, I am quite familiar with its strengths and weaknesses.  One of the weaknesses that always should be looked at carefully when evaluating studies is the definition of your population.  For instance, there was a study in a Scandanavian country that provided beta-carotene supplements to smokers.  Lo and behold, they found no effect on prevention of cancer.  So they extrapolated way beyond the evidence and said that consuming beta-carotene rich foods didn't matter for cancer prevention.  Yet, this population ate large quantities of fish -- so their livers were probably saturated with retinol (the animal form of vitamin A).  The response to beta-carotene might be completely different in a country like Niger where even the goats are vitamin A deficient because the greens are so dried out.  

So, I am disturbed by the extrapolation of a study of a general population of infants using nipple shields to a specific population of infants who have been carefully screened and evaluated for appropriate use of the nipple shield.  

I think this problem goes to the problem of "risk" versus "response". There once was a study that screened for risk factors for low birth weight.  They intervened with a high protein diet thinking it would reduce the low birth weight.  They actually saw an increase in low birth weight.  The reason why they saw an increase was that the predominant risk factor for low birth weight in this population was smoking.  A high protein diet won't compensate for smoking because the mothers weren't at risk from a low protein diet.

To extend this to infants and nipple shields.  If you have a population of infants who do not have problems with jaw stability or muscle tone or untreated ankyloglossia, you may very well find that the nipple shield will not help them and may even be detrimental because they do not need assistance with milk transfer.  They need appropriate positioning so that they can drink well.  If, however, you screen for specific problems, only use the nipple shields for those specific problems, work on the underlying problems, and remove the nipple shield when it is no longer helpful, you may very well find that you IMPROVE milk transfer.

I actually do have a great amount of clinical data to support the fact that among a subpopulation of FULL TERM infants there is IMPROVED milk transfer with nipple shields.  Milk transfer can be easily checked.  The interventions for a specific population should NEVER be based on the interventions for the GENERAL population.  Tools should be targeted for their appropriate use and when this is done they remain "tools" and not "gadgets" as Linda Smith often discusses.

Sincerely,

Susan E. Burger, MHS, PhD, IBCLC

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