Breastfeeding Medicine

Physicians blogging about breastfeeding

Trust and test weights

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“Nobody seems to trust test weights in our unit.  What are we doing wrong?”

To “test weigh” a baby means to measure how much milk she has transferred by simply weighing her — clothing, diaper and all — before and after breastfeeding.  Test weights are often used in term infants using precise scales such as the Medela BabyWeigh.  A few studies have supported the utility of test weights in preterm infants: these include a Swedish study favorably comparing babies cared for in NICUs using test weights vs NICUs that did not (earlier attainment of exclusive breastfeeding and earlier discharge) as well as a small study from the illustrious LCs at my own institution describing the development of a technique for accurately performing test weights.

It still seems, though, that NICU providers and even parents have a tendency to distrust test weights in premies learning to breastfeed.  Some of this distrust, especially for the providers, is probably a residuum of earlier studies using less precise scales and/or less consistent, accurate weighing techniques.  (It is true that we NICU folks tend to love our numbers, and we prefer that they have as many significant digits as possible.) I suspect another large part of the distrust has to do with the fact that premies who are learning to feed don’t consistently transfer the same volume of milk even when their feeding quality seems to be subjectively “good.”  As with learning to walk or talk, learning to feed is an incremental and not a linear process… but when numbers-focused, pattern-seeking people see “inconsistency” in the amount transferred, we think “that can’t be right.” Finally — just perhaps — part of the distrust might be with breastfeeding itself.  If we can’t measure it or control it, we can’t trust it. And if parents hear us expressing distrust of breastfeeding, they are probably more likely to distrust it as well.

Fortunately, a new study in the Journal of Pediatrics provides new support for the distrusting among us. This group took the breastfeeding out of the picture altogether: in a larger number of premies, using the protocol developed above, they performed test weights before and after gavage feedings.  (This means that the volume given was known, and the test weight was compared to the volume given.)  They found that 85% of the test weights were within + 5mL, which is clinically acceptable for older premies (>34 weeks).   I admit to glossing over the finer details here and encourage anyone who is interested to read the paper more closely.  But knowing that test weights do correlate with a known volume given by gavage, there is no reason we shouldn’t be able to trust them in measuring “unknown” milk transfer at the breast.


Bottom line: be consistent in your weighing procedure, use a good scale, and… trust the babies as they learn to breastfeed. If we trust the babies, we can empower their moms,  which is one of the most important parts of our job.  NICU moms need to be able to trust themselves and their babies, not just their NICU providers!

Kimberly Lee is a neonatologist and member of the Academy of Breastfeeding Medicine. 

Posts on this blog reflect the opinions of individual ABM members, not the organization as a whole.

Written by neobfmd

January 6, 2017 at 4:46 pm

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