Science You Can Use: Flawed study says early formula use increases exclusive breastfeeding

Supplementing with breastmilk, not formula, is the best way to go when medically indicated.

A new study making headlines this week suggests that “early limited formula” use actually increases the chances that babies will be exclusively breastfeed later on.

This small study enrolled 40 full-term newborns between 24-48 hours old who had lost more than 5 percent of their birth weight.  Their mothers had indicated their intent to exclusively breastfeed (but appear to have been okay with supplementation for the purposes of this study).  The babies were assigned either to receive formula, consisting of one-third of an ounce of infant formula–about 2 teaspoons–fed by syringe following each breastfeeding, or to continue breastfeeding exclusively. The babies receiving stopped using it when their mature milk came in.

The results:  At the one week, all the babies in both groups were still breastfeeding. But only 10 percent of the babies who had received formula in the hospital were also using formula.  Of the mothers who had exclusively breastfed in the hospital, 24% were using formula.  At three months, the researchers found a similar difference, with 79% of the babies who had received formula breastfeeding exclusively, compared with 42% of the babies who had not received formula.

You may already have picked up on a few problems with this study.  I’ll run through the ones that are the most salient.

Prior research shows that use of formula without medical indication strongly undermines breastfeeding.  This study contradicts decades of prior research, which has demonstrated that early supplementation is associated with shortened breastfeeding duration.

In fact, one recent study found that, of the Ten Steps to Successful Breastfeeding (the basis of the Baby Friendly Hospital Initiative), early supplementation had the most powerful negative effect on breastfeeding rates.  Using CDC data, this study found that having a baby in a hospital which didn’t follow Step 6 (no supplementation without medical indication) was associated with a 10.5 week shortened duration of breastfeeding.

The wrong criteria for newborn weight loss.  Newborn weight loss averages 7%, and intervention isn’t considered necessary unless weight loss exceeds 10%, according to the American Academy of Pediatrics. What problem was this study trying to solve by supplementing babies who had no medical indication for it?

Why try this?  We already know what works.  We already know how to improve breastfeeding rates without the use of formula, and we have known it for some time.  The Ten Steps to Successful Breastfeeding increase breastfeeding duration and exclusivity, and they’ve been around for over 20 years.  But 94% of babies in the U.S. are being born in hospitals which are not Baby Friendly.  And 4 out of 5 hospitals say that they supplement more than 10% of their babies for no medical reason.

Here’s one recent demonstration of the effect of following evidence-based practices, and there are more.  A 2008 CDC study found that “compared with the mothers who experienced all 6 “Baby-Friendly” practices, mothers who experienced none were ∼13 times more likely to stop breastfeeding early.”  Note that this was just 6 of the 10 steps.  The effect of all of the steps would likely have been even greater.

Sample size too small, no controlling for other factors.  This study enrolled only 40 women.  That number makes the conclusions far less reliable than prior research which has examined patterns of thousands of women.  And because the number of women in the study is so small, the authors weren’t able to control for a number of factors known to influence breastfeeding patterns, such as age, income, race, education, parity, and prior breastfeeding experience.

One author has financial ties to formula companies.  One co-author disclosed that he has been a paid consultant to Mead Johnson and Abbot Laboratories, the two largest formula companies operating in the U.S.

Milk came in late for one quarter of the mothers.  Mentioned in the study but not explored was the fact that one in four of the mothers experience a delay in their milk coming in, defined as later than 72 hours.  That’s an indication that there is a problem, and it’s associated with less exclusive breastfeeding long term.  The babies in the formula group got formula, which probably addressed any fussiness on the part of the baby.  Once their milk came in, off they went.

For the mothers in the no-formula group, they were left to fend for themselves.  Picture this:  For these mothers, their milk came in late, they got home and had babies who were freaking out, and it naturally undermined their confidence in exclusive breastfeeding.  Is it any wonder that they turned to formula?  And as the authors point out, once you’re using formula at one week, you’re more likely to be using it at two weeks, and 1 month, and 3 months.  All of the moms whose milk was late coming in should have gotten help establishing lactation, supplementing with their own milk (as show in the image above), and a careful evaluation of supplementation if the baby’s weight loss exceeded 10% consistent with the Academy of Breastfeeding Medicine’s supplementation protocol.  That would have put them on an even playing field with the other moms, and you may have seen different outcomes as a result.  The no-formula group also got a lesson in soothing techniques, to even out the amount of contact each group got from providers.  As Dr. Alison Steube notes, this may have “telegraphed” a lack of faith that exclusive breastfeeding would work out, further driving the tendency of these moms to use formula.

Using formula to supplement instead of human milk.  The number one rule is feed the baby, the number two rule is use the mother’s expressed milk, or donor milk, when possible.  Using a mother’s expressed milk can boost her confidence in her own ability to feed her baby; using donor milk can underscore the superiority of breast milk to any milk substitute.  Wouldn’t this study have been different if it was about the “Effect of Early Limited Human Milk Supplementation on Duration and Exclusivity of Breastfeeding in At-Risk Infants”?

Undermining recent progress.  There are significant efforts underway to reform hospital practices in ways we know to be supportive of breastfeeding.  Prior evidence shows that early supplementation undermines breastfeeding.  So in our view it would be irresponsible for hospitals to switch directions on the basis of a single study of 40 women.

Editor’s Note:  We are very disappointed that the New York Times article failed to include skepticism from highly regarded health experts.  Disseminating the results of this flawed study as “good news for mothers” is irresponsible journalism.   Please read Alison Stuebe, MD’s excellent article, and see the quotes by neonatologist Kathie Marinelli, MD in the TIME.Healthland article.  

Image credit:  Wikimedia Commons

9 thoughts on “Science You Can Use: Flawed study says early formula use increases exclusive breastfeeding

  1. One other problem that I see is that they used mothers who ALREADY DECIDED to exclusively breastfeed. There is a different mindest with a woman who INTENDS to breastfeed and a woman who intends to formula feed. Just Saying….


    1. Yes! I was thinking the same thing – that these women may already be the type of mothers who would choose to continue breastfeeding anyway, rather than revert to formula.

      Great post! I agree with all of these analyses.

      ALSO, it doesn’t appear that they looked at type of birth – cesarean, etc.


  2. My experience is that once “supplements” are recommended, the amount of the “supplement” is 1 to 1.5 oz of formula per feeding.

    Well if you’ve got an 8 lb baby who is being fed 10 times per day…that is 10-15 oz of formula…for a baby that would only be taking 16-20 oz of formula if being straigh formula fed. So what then is the “supplement?” The 10-15 oz of formula, or the 1-10 oz of breastmilk? But pediatricians who see the headline that “formula supplementation helps with breastfeeding” and don’t read the article will feel confident that they can continue on with recommending large “supplements” rather than the 1/3 oz used in the study.

    Not surprisingly, my experience is that the vast majority of women I’ve seen who have followed this level of “supplementation” end up completely weaning before the baby is even a month old.

    I do question the comment in this blog post about milk not coming in by 72 hours being a “problem.” I read a study recently ( ) that found that 41% of women did not have their milk come in until after 72 hours. If it is happening this frequently, certainly it must be within the range of normal for it to take over 72 hours for milk to come in?


    1. Yes, I too thought that 41% would make 72+ hours seem like the norm, but then I remembered that one in three births (one in four in Canada, where the study was conducted) is by cesarean, and cesarean birth causes a delay in lactogenesis II. And there are other common demographic factors (age, obesity) and obstetrical practices (pitocin, pain medication) that are associated with late onset of mature milk. So it may be quite common, but it’s probably not the physiologic norm.


  3. The intervention was clearly not medically indicated, and the study does not state that. They only talk about a 5% weight loss without any explanation as to its significance. Interestingly, babies with 10% weight loss were excluded from the study – the only medically indicated instance. I read it and thought it was a psychological intervention for mothers to see if easing their anxiety about the hunger of their newborn made them more relaxed and ready to breastfeed, but the study was not at all presented that way. I hope enough medically qualified researchers will debunk this study. Thanks for your posting.


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