If you are using baby bottles, they must be sterilised between uses. This is true whether your bottles contain expressed breastmilk or formula. This is due to the potential presence of cronobacter sakazakii bacteria. This is a bacteria that is commonly found in the environment and has been known to cause severe and often fatal meningitis or sepsis in young infants.

It can linger in contaminated powdered infant formula or on the surfaces of baby bottles and expressing equipment. If this bacteria is present, standard washing is not enough to destroy it, and therefore we must sterilise all equipment connected to infant feeding.

Before sterilisation, all bottles, teats, and expressing equipment must be thoroughly washed up using these steps:

Clean all bottles, teats, and other equipment in hot, soapy water (preferably soon after use).
Use a specialist bottle brush to clean inside the bottles (and only use this brush for bottle cleaning), and a smaller teat brush to clean inside the teat or other small pumping parts.
Rinse all parts in clean water to remove the soap.

To sterilise, there are three main methods that you can choose from:

Steam sterilising. For this method, you can use either a microwave kit or a specialist steam steriliser. If you’re purchasing a kit, it is helpful to purchase the same brand as the bottles that you own, as the'slots' for each bottle part will fit more exactly when sticking with the same brand. Both of these use heat (steam) to kill the bacteria. Follow the specific instructions on your kit as to how much water to add and how long the sterilisation process takes.
Boiling sterilising. First of all, make sure that all the parts that you are sterilising are suitable for boiling. Boil all the feeding equipment in a pan of boiling water (with all parts submerged) for 10 minutes. Please note that teats will need more frequent replacement with this method, so keep an eye on them for signs of wear. Do set an alarm to remind you when the 10 minutes are up so you don’t accidentally boil until the water is dry (which can destroy the bottles and be a fire hazard).
Cold water sterilising solution. The steriliser should have instructions for making up the sterilising solution, which must be followed. Submerge all feeding equipment into the solution, taking care to ensure that there are no air bubbles within the bottles or teats. The kit should come with a plunger to ensure that all the equipment remains submerged. Standard time in the solution is at least 30 minutes, but check the manufacturer guidelines in your kit. Sterilising the solution should be changed every 24 hours.

Once sterile, how quickly must I use the bottle?

When we discuss sterilising the bottles, we are actually deep cleaning the bottles rather than making them medically sterile. As discussed above, the cronobacter bacteria are potentially deadly and need to be destroyed. Once this process has happened, the bottle will remain suitable for use whenever you next need it. This is provided that it is kept in a clean place away from any other contaminants. It can be helpful (assuming you have the space) to dedicate a corner of the kitchen to bottle cleaning and sterilisation to prevent contamination from infant formula powder or other foodstuffs or cleaning supplies.

How do I sterilise my baby’s bottles?

For our Baby Feeding Journey, Unii Expert Wendy Lever shares how to sterilise baby bottles.