Bacteria in donor breastmilk? An examination of the data...

A report in Pediatrics (the official journal of the American Academy of Pediatrics) was released on Monday revealing the results of a study done on bacteria found in breastmilk purchased online.  This report has attracted a wave of media attention.  I will be compiling a list of responses to this study over the next few days.  But firstly, I am hosting this guest-blog response written by a friend of mine with experience in biomedical research.

Milk Selling? Or Milk Sharing?

by Jenna Tress 

Jenna has almost 15 years of biomedical research experience 

A study that claims to look at both milk selling and milk sharing has captured the media’s attention the past few days after being published in Pediatrics. There are several issues with this story, the media’s portrayal of it, and the study itself. Importantly, the results of the study are not applicable to milk sharing, for several reasons.

"Milk sharing" and "milk selling" are used as and treated as interchangeable, yet there is no proof put forth that these communities are equivalent populations, in make-up, hygiene practices, infection rates, etc. It is a fallacy to simply assume that the populations are equivalent.

There is a very large selection bias, even within the sample that was chosen. Arrangements were terminated under a whole host of conditions, thereby creating a non-equivalent selection of samples. 495 inquiries were sent, and their final sample was 102. If a selling mother asked about the infant, wanted to speak on the phone, or essentially have any contact outside of the anonymous shipping to a PO Box, the transaction was terminated. One of the principal tenets of peer-to-peer milk sharing is building community, and having mothers connect with each other.

Samples were shipped. This is, again, not equivalent to many/most  peer to peer milk sharing arrangements, which are locally based and delivered in person (at a rate greater than 90%, based on preliminary research), thereby greatly decreasing the amount of time they are out of the freezer, and then decreasing the likely rate of bacterial growth, as each transit day was associated with an increase in bacterial count. There was also no control of the mailboxes, so the samples that had already been in transit for several days could have sat there with no pick up. While information was collected upon collection of the samples, there is no data submitted as to the time between delivery and pick up.

The researchers in this study compared 20 milk bank samples to 102 purchased samples. Even stated in the paper is that the power of the milk bank samples is quite suspect. Comparisons between the two should not even be made.

There is huge variation of samples that has been observed previously, as the authors point out. The Chinese study cited had 86% contamination rates, and the rate of actual infection in the infants was not reported here. Following from that, the actual likelihood of the prevalence of infection is not even broached. Even if there is gram-negative bacteria (at several days post-shipment, with improper handling at the point of reception additionally) at a high rate, what, then, is the real risk to the infant? One would expect an equivalent infection rate, or a whole rash of very sick babies and alerts from authorities, but this does not happen, or it would have come out sooner.

Not explored within the paper, as well, is the fact that we know that even milk directly from a mother’s breast has a lot of bacteria in it, which helps with gut development. Extrapolating from the results of this small, biased study is research folly.

A take home message from this study that should be emphasized to all breastfeeding and pumping mothers, regardless of how or why their milk is used, be it for their own children, to donate, or to sell, is that proper and sanitary hygiene should be used at all times. There are also risks inherent to the use of formula, especially when not prepared properly (i.e., with clean water heated to proper temperature, proper sanitation of bottles, etc). All of life is risk management and mitigation. This study does not put forth further help or knowledge about milk sharing, rather, it fear mongers and attempts to put a biased spin on the growing movement of mothers sharing milk.