06/20/2021
Have you ever wondered if the markings on baby bottles and storage bags are correct? Well, this is what I pondered on this beautiful Saturday. I spent HOURS figuring this out, and I thought I would share with you!
If fluid is measured by the markings on infant feeding bottles, do those markings show the actual fluid amount that is being poured in?
I chose to measure 4oz, because I work in the US, and the bottles here have oz markings.
I used 19 common infant feeding bottles, storage bags, and passive silicone pumps. 16 brands were represented. Two vacuum pumps, five storage bags, and 12 bottles
I measured what appeared to be 4oz of fluid into each vessel. I weighed the fluid, and noted the difference between the weight 4oz truly should be, and what it was in each vessel. I decided to measure the differences in ml because I am European, and although I live and work in America, the metric system is what makes sense in my brain.
My findings:
Only two bottles were exactly correct.
14 of the 19 vessels under estimated how much was in them.
Three of the 19 vessels over estimated how much was in them.
If using a margin of 5% +/-, 11 of the 19 vessels fell within that margin. Only one storage bag fell within the margin.
If a family would measure out a daily 709ml (24oz) for their baby in these vessels, they would in reality be feeding from 79ml (2.6oz) less than expected, to 18ml (0.6oz) more than expected.
If a family would measure out a daily 1062ml (36oz) for their baby in these vessels, they would in reality be feeding from 81ml (3.9oz) less than expected, to 27ml (0.9oz) more than expected.
For families who feed mainly from the breast, these numbers really do not mean enough to worry about. But for formula feeding families, and for pumping family, these numbers are worth noting.
Many families do not receive good education on how to safely reconstitute powdered formula (Always use HOT water when you reconstitute infant formula. Use hot , almost boiling, water to kill any bacteria that can grow in powdered formula. Do not use cold water. ALso, always measure the water before adding the powder* edited to add, please be sure to use safe water for preparation of infant formula. If your tapwater is unsafe, please use bottled water.* Using the correct water volume when reconstituting formula powder is another thing everyone should get educated on.
If a pumping family separates their daily milk yield into freezer bags, going by the measurements on the bags, these babies will most likely be getting less than what their parents think they are getting. Parents should be educated to not always rely on the measurements on freezer bags.
Today I spent some time doing the entire experiment over again. I had most bottles of the same type vary by one or two grams. I also had most of the storage bags be one or two grams off from the same as I recorded the first time.
***updated after doing the experiment several more times***
Coming into this experiment I had all kinds of theories myself, and I was kind of amazed that they did not translate to reality.
The only bottle that showed correct measurements, and consistently stayed the same, was the 5oz Parents Choice bottle. Yeah. I was floored.
The storage bag that consistently stayed the same, and only a gram off, was the Target bags. Equally floored.
Whichever bottles you use, I would love for you to do a little experiment. Weigh the milk you plan to feed, for just a few feeds, and see how your bottles stack up. You can keep using whichever bags and bottles you have, but pay attention. Pay attention to your baby. Follow their feeding cues. Pay attention to the difference between the bottles you use.
