Questions and answers on inaccurate markings on baby bottles

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What is the problem?

Some caregivers may be using feeding bottles for babies with inaccurate volume markings, which mean they could be unintentionally feeding their babies infant formula that is too concentrated.

A survey by Consumer Affairs (part of the Ministry of Business, Innovation and Employment) has found that a number of baby bottles sold in New Zealand have incorrect volume markings on them.

Of 35 bottles tested, 15 had volume indicator markings that were inaccurate by more than five percent. Some bottles overestimated the volume of fluid in the bottle by up to 40 percent.

This means that the 100 ml mark on the bottle would actually be only 60 ml in volume.

The inaccurate bottles tended to be cheaper, un-named brands purchased from discount shops.

What does that mean for babies?

Formula that is too concentrated can cause problems like vomiting, diarrhoea and constipation. Untreated, this can cause serious dehydration.

Formula that is too concentrated will provide excess energy (calories) and other nutrients. 

Over time this could lead to overweight or obese babies and toddlers. It could also harm organs such as the kidneys, when they are still immature.

Could this be a problem for all babies who have infant formula?

Yes, but it is especially a problem for younger babies, that is, babies six months of age and younger. Older babies are bigger and have more mature organs. Also they will be eating food and possibly drinking water from around six months of age so are not so dependent on formula for all their food and fluid needs.

But won’t baby stop feeding once baby has had their fill?

Yes usually, but baby may feel full sooner due to the more concentrated formula and may stop drinking before he or she has had enough fluid. This could cause baby to become dehydrated.

On the other hand, baby may keep drinking to quench his or her thirst. This could mean baby takes in too many calories and nutrients because the formula is too concentrated.

Did all of the inaccurate volume markings result in over-concentrating infant formula?

Most did, however, four bottles had inaccurate volume markings that resulted in over-diluting the infant formula by between 6 and 10 percent. 

Infant formula that is too diluted (too much water added) could result in babies not getting enough energy (calories) and nutrients. Long-term under-nutrition can lead to delayed growth and development.

Are there any baby bottles with accurate volume markings?

Yes – bottles that state on the packaging that they comply with the EN14350 standard or have EN14350 stamped on the actual bottle should be accurate. This is a European standard that requires bottles filled to the 100 ml mark to be accurate to within five percent.

I’ve got a household measuring cup or jug – can’t I use that to measure the amount of water required?

While these cups and jugs are suitable for baking and general kitchen use, they are not accurate enough for measuring small amounts of fluid, such as for making up infant formula. As a result we don’t recommend using them to measure the water needed for infant formula.

I don’t have any bottles with the EN14350 label or mark on them, what should I do?

Pharmacies have access to what are called trade-quality measuring equipment and can check if your baby bottles are accurate.

You can take your baby bottles to a pharmacy and ask a pharmacist or other member of staff to check if your bottles are accurate. Then, if necessary, pharmacies will be able to mark the correct volume levels on your bottles. Note that pharmacists may charge a fee for this service.

The Ministry of Health has been working with the Pharmacy Guild to ensure that this is possible and that pharmacy staff can help you.

I’m breastfeeding – does this affect me?

The Ministry of Health recommends all babies are exclusively breastfed to around six months of age, and continue to be breastfed for up to one year of age or beyond once complementary foods are introduced. 

For those babies not fed breast milk, infant formula is the only appropriate milk alternative up to one year of age. 

If you are breastfeeding your baby this issue does not affect you.

If you are expressing breast milk to feed your baby and want to know the accurate volume being expressed or given either use an EN14350 bottle or check the accuracy of your bottle or measuring containers with your local pharmacy.

Why don’t you make it mandatory for bottles sold in New Zealand to meet that standard?

The Ministry of Business, Innovation and Employment (MBIE) advises that this issue falls outside of the scope of current consumer law. 

The provisions of the Fair Trading Act 1986 allow mandatory standards relating to products which may cause injury. Baby bottles which do not meet the EN14350 standard are not in themselves unsafe, rather they may have the potential in some cases to lead to adverse health effects. 

The Weights and Measures Act 1987 does not offer a remedy as it relates to measurements in trade transactions, so does not cover inaccurate markings on baby bottles.

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