Inaccurate volume markings on baby feeding bottles

Advice for health practitioners

Ministry of Health policy

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. 

The issue

A survey of the accuracy of volume markings on feeding bottles for babies by Consumer Affairs (part of the Ministry of Business, Innovation and Employment) has found that a number of bottles sold in New Zealand have inaccurate markings. 

Of 35 bottles investigated, 15 had volume indicator markings that were inaccurate by more than five percent, including some bottles that overestimated the fluid volume by up to 40 percent.

The inaccurate bottles tended to be cheaper bottles purchased from discount shops.

As a result, if using the volume markings on a baby bottle as a guide to how much water is needed to make up formula, caregivers could be unintentionally over-concentrating formula by between 5 to 40 percent.

Unintentional over-concentration of infant formula can have short and longer term negative effects for the infant. In the short term, the infant may not tolerate the formula.  Problems like vomiting, unsettled tummy and diarrhoea and/or constipation can occur.

If untreated, this can cause serious dehydration.

Long-term inappropriate concentration of formula will provide excess energy and other nutrients.  This could lead to overweight or obese infants and toddlers.

Inappropriate concentration of formula could potentially cause organ damage as a result of long-term intake of higher levels of nutrients on immature organs.

There is a European standard for baby bottles which means that the 100 ml mark is accurate to within five percent  – however these EN14350 standard bottles are usually more expensive than bottles sold at discount shops.

What is being done about the issue?

The Ministry of Health has been working with Consumer Affairs (Ministry of Business, Innovation and Employment), the Pharmacy Guild, Plunket and other providers, as well as the Infant Nutrition Council (INC) and the bottle manufacturers industry, to develop a way of helping parents and caregivers ensure babies receive infant formula at the correct concentration.

Regulation controls the accuracy of measurement indicators in equipment sold for trade purposes, but there is no mechanism to control the accuracy of measurements in equipment sold for domestic use.

While household measuring 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.

Health practitioners need to be aware of this situation and explain the risk to caregivers who use infant formula.

To ensure the volume markings on baby feeding bottles that do not carry the EN14350 standard are accurate, the Ministry of Health and Consumer Affairs (Ministry of Business, Innovation and Employment) will recommend parents and caregivers get them checked by their pharmacists who have access to ‘trade quality’ measuring equipment.

This will mean that a corrected measurement can be marked on a bottle for future use.

More information is available at Questions and answers on inaccurate markings on baby bottles or contact Elizabeth Aitken at the Ministry of Health 04 496 2000.

More information for the public can be found at Formula feeding in the Your health section and by ringing PlunketLine 0800 933 922.

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