AYESHA RASCOE, HOST:
For years in the U.S., the guidance around breast milk has been pretty clear. If there is any breast milk left over in a bottle after a feeding, the leftovers must be thrown away within two hours to protect the baby's health. But recently on social media, some parenting influencers have been questioning that advice. Here to explain the science of breast milk storage safety is NPR health correspondent Maria Godoy. Welcome.
MARIA GODOY, BYLINE: Thank you, Ayesha.
RASCOE: So, Maria, look. What are the risk of reusing a leftover bottle of breast milk?
GODOY: You know, the main concern is bacterial contamination that could potentially make a baby sick. So when a baby feeds from a bottle, bacteria from their mouth can get into the bottle, and then it'll continue to multiply. And the idea is that the longer the bottle sits, the more the bacteria will grow. And then there are also bacteria that can be introduced at any point during the process. And that's why guidelines from the Centers for Disease Control and Prevention and other groups recommend that you always wash your hands before pumping or handling breast milk and, you know, clean your pump parts after every use. And once you feed the breast milk to the baby, if there's any left over in the bottle, the CDC says you can give it to the baby up to two hours later and then toss it out to be safe. But, you know, pumping is really hard work.
RASCOE: It's another job. And, you know, the little bit that I did, I did not like it.
GODOY: Oh, no. It takes a lot of time and effort, and it can be emotionally and physically exhausting. So the idea of throwing away that breast milk is kind of crushing for some moms, which is why I think a new unpublished study from Hannover Medical School in Germany suggesting that milk might be safe for longer than two hours has gotten a lot of attention in parenting circles and a lot of pushback, too.
RASCOE: Well, what did the study find exactly?
GODOY: So researchers recruited parents to feed their babies a bottle of breast milk, and then they tested the microbes in the milk before it was fed to the baby and then at various time points after. And they found there wasn't really any significant bacterial growth in the milk from the time the baby finished eating up to eight hours later.
RASCOE: Well, I mean, that sounds like good news. So why the pushback?
GODOY: Well, the study hasn't gone through peer review yet, and the sample size was small - only 17 infants who drink breast milk. But some parenting influencers basically ran with it and said, yeah, go ahead and ignore the guidelines. Don't toss that milk. I spoke to Jennifer Yourkavitch. She's a breastfeeding researcher at the University of North Carolina at Chapel Hill, and here's what she said.
JENNIFER YOURKAVITCH: You know, human milk has a lot of antibacterial properties or anti, you know, spoilage properties. So it doesn't surprise me at all. It's a promising finding. It's not enough to change a guideline.
GODOY: Yourkavitch says we really need a lot more research into this issue, but there's just not much funding for that. I also spoke to April Fogleman. She's a researcher with NC State who also did a small study on leftover breast milk, and she says guidance needs to err on the side of being conservative because there are so many different factors involved.
APRIL FOGLEMAN: How old is your baby? How healthy is your baby? How long was the milk stored? How well did - were the pump parts cleaned?
GODOY: With so many variables, she says, it just makes sense to play it safe and toss that milk after two hours.
RASCOE: So what's the takeaway for parents?
GODOY: A few things. For one, I think, you know, don't listen to just whatever you hear on social media, and that goes for a lot of things. But also, as Fogelman told me, pumping is demanding. So just do the best you can to follow the CDC guidelines. But again, breast milk does have antimicrobial properties, so if you mess up, give yourself some grace.
RASCOE: That's NPR's Maria Godoy. Thank you so much.
GODOY: My pleasure.
(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.
NPR transcripts are created on a rush deadline by an NPR contractor. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.
