I learned the hard way…
This is a special post for you brainy business babes who are (or will be) moms!
I’ve been nursing my daughter, Baby P, for nearly nine months. That entire time, I used Medela bottles to feed her and store milk. This morning, on a whim, I decided to try sending her milk to daycare in an Avent bottle I bought several months ago, but had never used.
I was surprised when I poured 4 ounces of milk from the Medela bottle into the Avent bottle – it fell way short of the 4-ounce mark. I topped up the Avent bottle and carried on with my day… but I couldn’t get this nagging thought out of my head: which bottle was correct?
Being a bit of a science nerd, I decided to go all fourth-grade-science-fair and do an experiment. Here are the two bottles, you can see that each of them is filled exactly to the 4-ounce mark (using US ounces).
(FYI – the liquid in the bottles is water with a bit of blue food coloring to make it easy to see. If my breastmilk was actually bright blue, this would be a whole different post.)
I rummaged through my bin of random baby stuff I got for free when Baby P was born, and found these two unopened Gerber disposable nursers, which hold 60 mL (2 ounces) apiece. Perfect for my impromptu science experiment!
Here are the results:
You can see that the Avent bottle measures exactly 4 ounces, but the Medela version of 4 ounces is actually 5 mL short.
That may not seem like a big deal, but if you are giving your baby six 4-ounce bottles a day and losing 5 mL each time, you are feeding that little one a full ounce less every day than you thought you were!
And that’s if you are being an absolute stickler for measuring exactly to the 4-ounce line. I confess that, as a sleep-deprived new mom, I mostly eyeballed it.
This explains some strange things that were happening to us – like when Baby P seemed so much hungrier when I traveled out of town. And I REALLY wish I had known about this early on, when the doctor was worried that Baby P wasn’t gaining weight.
That’s why I’ll never use Medela bottles to measure milk for my baby again. I encourage you to test your bottles too and let me know what you find!
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A few notes, for those who really like to get into the weeds:
– I tested 3 different Medela bottles and 3 different Avent bottles and got the same results.
– I also tested the measurements using my Pyrex kitchen measuring cups and found the same thing.
– I have also been using the Medela freezer storage bags all along and never noticed a discrepancy, so I have to assume their measurements are wrong too. Maybe one of you will test it and let us all know 🙂
– I have not received any kind of payment or free stuff or anything from Avent (or Medela, for that matter). I have not included any affiliate links in this post. I really just want to get the word out to other moms about this!