Sarah Norris – The Baby Detective

Baby Bottle Basics
January 31, 2017

Baby Bottle Basics

A simple explanation of bottles, teats and anti-colic features.

(this article is based on bottles available in the UK but should still be useful for other parents and carers in other countries because the main features remain the same, and you will gain insight in to how and why the bottles work as they do)

My aim in writing this article is to try and clear up some of the confusion about baby bottles.

There are so many different makes and models, by different manufacturers, all using complicated terminology and making various claims about their bottles latest features, that trying to choose ‘the right bottle’ can become very stressful. If you couple this with some of the current heated debates and campaigns about feeding methods and all the ensuing emotions that this stirs up, it is easy for people to lose sight of the primary function of any bottle, which is to get food or liquid into babies.

If you are reading this I am assuming you have an interest in using bottles at some point and, therefore, any debate about whether babies should be breast or bottle fed is totally irrelevant. However you choose to feed your baby is your choice and is no business of myself or anyone else, and I support you completely.


One of the comments I have heard is that bottles are an unnatural and modern invention so I did a bit of research and found that, far from being modern, baby bottles, in one form or another, have been used throughout our history.

The earliest known baby feeder is an earthenware teapot style from 2000BC which is around the end of the Stone Age. This is amazing, more so if you realise that this is quite an advanced design and so was obviously being developed for quite some time before this one was made. I think it logical to infer that many, many previous types of feeder had been used leading up to that point.

The mummified remains of 3000 year old Cherchen Man and his family, found in Xinjiang in Western China, revealed a baby buried with its bottle, made from a sheeps udder.

Terracotta feeders from 450 BC were used by ancient Greeks to give wine and honey, whilst European woodcuts from the 13th and 14th Century show babies feeding from cow horns which used teats made from leather or dried cows teats.

The earliest forms such as dried sheep udders would have been available to the very earliest of our ancestors and all the evidence suggests that bottle feeding has been going on for as long as man has been recognisable as man, and is, therefore, no more ‘unnatural’ than any other form of tool using, just something they did to help their families survive.

Modern Bottles

Please forgive me if you find this too basic or over simplified, but I did meet a father who was surprised to hear that teats had different flow rates, so, to be thorough, I am going to assume no prior knowledge regarding bottles and explain all their features in turn, with regards to function and practicality for everyday use and different situations.

Baby bottles usually consist of

  • A reservoir for the milk,
  • A measuring gauge,
  • A teat that delivers the milk to the baby’s mouth,
  • A screw on collar that attaches the teat to the bottle
  • A lid (until you lose them, or your older children take them to use them as pretend teacups or bath toys !).
  • An anti-colic feature.

The Reservoir, or body of the bottle.

The body of the bottles used to be uniformly cylindrical but are nowadays varied in shape, as you can see in the photograph below.

The bottles are either narrow necked or wide necked and need teats specific to that shape i.e a wide necked teat will not fit on a narrow necked bottle, but may just fit a different brand of wide neck.( All the bottles I have used for this article are wide necked).

The actual shape doesn’t affect performance except that narrow necks are harder to fill (especially in the middle of the night) if you are using powder formula which tends to spill everywhere, and they can be harder to clean (but not much, it’s just that some bottle brushes won’t fit). Apart from that it is just a matter of personal preference as to how they feel in your hand.

Bottles are made from plastic or from glass, though all the ones here are plastic. There was a recent scare about potentially harmful BPA’s in plastic bottles but most manufacturers now use BPA Free material so there is no health benefit to either type. I use plastic bottles because I fnd them lighter and less clumsy but that is just personal preference so just use whatever feels right for you and your baby.

All the bottles here are 4 oz/120 ml (sufficient for most newborns) but in most bottles you can sneak in an extra 1oz/30mls which is sometimes useful  just in case you need a bit extra, or if you haven’t yet bought the bigger bottles (usually 8oz/240mls) The Mam bottle, however, has no extra room, and the Dr Brown bottle, though large, has an actual fluid capacity that is limited by its anti-colic feature.

Measuring Gauge

The measuring gauge is there so you can see how much milk is in the bottle to start with, and so you can see how much your baby drinks and therefore, in theory, should be easy to read, but in reality this is not always the case as you can see for yourselves in the pictures below.

You have to bear in mind that you won’t always be feeding in a brightly lit room. Sometimes you will be in a bleary eyed, semi-conscious, sleep deprived state in the night, feeding in a dimly lit room.

You need big, simple numbers and level markers………nothing else !

I have, in effect, been doing night feeds for 25 years, so trust me when I say that, in the surreal exhaustion that is the night feed, you do not need to be looking for a spotlight and a magnifying glass to try to make out opaque numbers on a see through bottle, pale numbers, or tiny numbers obstructed by superfluous bunnies !!!!! (sorry for the exclamation marks, but this just drives me crazy!)

In the left hand picture below the 2 bottles on the right (Munchkin Latch and Tommee Tippee) are extremely easy to read. The 2 on the left (both Avent) have guages in blue so they are being masked a little by the background but are, in real life, also very easy to read.

The picture on the right (Dr Brown, Nuk and Mam) shows bottles with clear, embossed numbers and with opaque numbers, both of which are invisible against milk, and  a bottle where the guage is very pale and obscured by pictures, again, making it very difficult to read. It also has a white base that makes reading anything under 2 oz/60 mls impossible to measure which is particularly frustrating when dealing with a small baby that only drinks small quantities because all accuracy is lost.


Collars are fairly simple and standard and the only real problem occurs if they leak, just check you have tightened them sufficiently (but not overly tight). There was one bottle a couple of years ago that I absolutely loved, but the collar leaked, and sometimes flooded, totally unpredictably, and, though I persevered, in the end I just couldn’t stand the mess. The inconvenience of constantly having to changes mine or babies clothes, or wasting the mothers precious expressed breast milk meant I had to stop using it.

Teat – size, shape, texture, flow rate, identification.

Size – When I say size, I am referring to the very end part of the teat that goes in to the baby’s mouth.

This does seem to make a difference to some babies that are premature, have small mouths, or that just gag easily.

I’ve seen babies said to have ‘nipple confusion’ that were absolutely fine when a smaller teat was used and I suspect that this may have something to do with the fact that, at the breast, the baby sucks and pulls the flexible nipple in to its mouth gradually until it fits comfortably, so baby has time to adapt. With a more fixed shape teat on a bottle the baby sometimes has less time to adapt, especially if being fed by less experienced parents/carers, and may be more likely to gag but having said that, I have also seen breast fed babies gag on larger (or more enthusiastically proffered) nipples.

Other babies seem to prefer latching on to a larger teat (maybe more to grip on to, or just more comfortable?). Even the newest baby can have strong preferences, it is just part of their character, but generally they just need time and patience to give them chance to adapt.


There are 2 main teat shapes to choose from, standard (rounded) and orthodontic (flattened/angled)

This is mostly a matter of what suits the baby, what the parents prefers, or is dependent on what type of bottles you end up being bought or given.

As long as the teat doesn’t cause gagging the majority of babies are quite capable of adapting to any shaped teat just as they adapt to the mothers nipples which can, by the way, be quite different even on each breast.

My 2 favourite bottles (Munchkin Latch and Avent Classic) just happen to have standard teats so this is what I use most often, but I know other maternity nurses who prefer orthodontic teats so there is no real advantage to either, except perhaps that some new/overtired parents seem to have trouble remembering which way up some of the angled orthodontic teats go e.g hole turned up towards the top of the mouth.

Please note – Orthodontic teats do not, as the name implies, give any protective benefits for babies gums and later dental development. The term orthodontic was originally applied to babies dummies/pacifiers/soothers when it was realised that prolonged use could have a detrimental effect on tooth development. It is worth noting more recent research has shown that, under the age of 2 years of age, most problems caused by dummies/pacifiers are self-correcting within 6 months of cessation of use.

Cleft Palate – Orthodontic teats can sometimes be helpful for a baby with a cleft palate because the teat can be used upside down, and an extra hole made on the opposite side to the cleft, so directing milk away from the problem area.

Tongue-tie – this seems to be a very common problem at the moment and, according to several top paediatricians that I have spoken to, is seriously over-diagnosed, but in genuine cases can lead to a baby being unable to form a good seal around the teat or mothers nipple making feeding very difficult. I have spent quite a time searching support groups and forums etc. trying to find out what teat is recommended, but, unfortunately there seems to be no clear winner. Various specialists, carers and parents all seem to have varying successes with different teats so I’m afraid, like so much else with babies, it is a case of trial and error until you find out what suites your own baby’s particular needs.


Most teats today are made from silicon which stands up well to wear and tear and sterilisation, and has the added benefit of being clear so you see where the milk is in the teat or when the milk is nearly finished.

The teats may be quite rigid and firm in texture or very soft and pliable and no one type is better than any other overall, it is mostly down to what suits your baby, with most babies seeming able to adapt to either type.

However, many of the bottles that are marketed as being ‘more natural’ and ‘mimicking the breast’ utilise the softer teats and do seem to allow baby to recreate the same jaw motion as when feeding at the breast so I do tend to use those when supporting parents who are combination feeding ( using expressed milk or formula in a bottle in conjunction with breast feeding).

Flow Rate

Teats are made to deliver different flow rates depending on the size of the hole, or number of holes. Usually, the newer babies are happier with the slower flow teats, simple because it can take them a while to become efficient at feeding in the ‘ suck, swallow, breathe’ rhythm and if the flow is too fast the baby can become overwhelmed by milk volume and start to choke.

Be warned, there is absolutely no standardisation in teat flow and categorisation so do not expect one brand to deliver the same flow rate as another.

Most are labelled 1,2 and 3, but some use age e.g. 1 month, 1-3 months, and others are called variflow/variable flow either meaning that the flow changes depending on how hard the baby sucks, or that the hole releases more or less milk depending on which way up the teat is turned (a nightmare if tired and feeding in the dark as you can’t see which way up it is supposed to be and generally get it wrong !).

Knowing the flow of the teat you are using is very important because it will help you to investigate any feeding problems you encounter.

I will go in to much more detail in a separate article about problem feeds, but for now, I have listed below some of the scenarios where a particular flow rate may be beneficial.

Slow flow

Windy/colicky baby. This may make the feed calmer and slower, allowing the baby more time to get the feeding action right and so take in less wind.

Reflux baby. The slower the feed, the more chance for the baby to begin digesting the milk and for the stomach to empty itself as opposed to a faster feed where the stomach becomes very full very quickly, so putting pressure on the stomach valve and increasing the likelihood of vomiting.

Greedy baby. Fast and furious feeding usually ends up with the baby getting a lot of wind, so a slower flow gives baby a chance to settle to a calmer, more rhythmical sucking motion.

Overtired baby. They are much more likely to get agitated or frustrated just because they are overtired, so slower flow gives them less to get cross about (unless they are very hungry).

Sicky baby. The slower the feed the more chance the body has to register when it is full so baby is less likely to overfeed and posset back the unwanted milk.

Combination feeding. Babies can get lazy if the milk flow from the bottle is faster than the flow from the breast, which is often the case so, it can pay to use a slow flow teat and keep baby used to working for his food to ensure he doesn’t start rejecting the breast.

Faster flow

Premature baby. Babies that are premature or ill can have a weak suck and little energy for feeding so a faster teat allows maximum milk intake for minimum effort.

Tired/Sleepy baby. Faster flow can make for a quicker, easier feed useful for night feeds or if you are in a hurry.

-Impatient/Greedy baby. Some babies are just guzzlers and get frustrated and angry if the feed is too slow so a faster teat gives them what they want.

Medicated baby. Sometimes baby needs medication that thickens the milk, such as in the case of reflux, so a larger hole is needed to allow the milk to flow.

The only way to find out the flow rate is to test it yourself, so I filled all the bottles with orange juice and tried them out. They are arranged in the photo below, with the slowest flow on the left and the fastest on the right.

In order of flow, from slowest to fastest, Munchkin Latch, Tommee Tippee, Avent Classic, Avent Natural, Nuk, Dr Brown, Mam.

Antic-Colic Features

Imagine drinking from a glass bottle by putting your mouth around the whole opening. You would be able to drink at first, but then the liquid would stop flowing.

This is because a vacuum has built up inside the bottle and the only way to release this is by relaxing your lips, breaking the seal around the opening and allowing air in to the bottle so the liquid can flow again.

This is exactly the same thing that happens with baby bottles and, when the flow stops, the baby instinctively releases the seal briefly around the teat to allow the pressure to equalise, before resuming feeding. However, the equalising action also allows air in to the baby’s mouth which they can then swallow when they next start drinking, and this is how your baby gets wind. (Note – Contrary to popular belief, this also happens during breastfeeding so breastfeeding babies also need thorough winding)

The idea behind all anti-colic features is to allow air into the bottle at the same rate as the baby is sucking the milk out, so no vacuum builds up and the milk flows at a uniform, steady rate. This means baby is less likely to need to break the seal and does, in my experience, lead to a calmer, more consistent feed, which in turn leads to a reduction inthe amount of wind swallowed.

Most bottles nowadays incorporate some sort of anti-colic feature, however, they are of varying designs and complexity. I spent quite a bit of time looking, but could find no scientific evidence that suggests any one design working better than any other, just anecdotal and personal preference.

Some designs utilise a one-way valve in the base of the teat to allow the air to enter, whilst others use a gap in the collar and it is worth knowing if this is the case because you should then be careful not to overtighten the collar and block the air flow.

More complex features use structures that sit in the collar of the bottle and project down in to the reservoir which I have to admit are my own least favourite type. Fisrtly, because they are all very fiddly to clean, having small holes requiring a separate tiny bottle brush to clean which I find irritating.  Secondly, because when you put hot water in them they tend to siphon the water back out through the anti-colic part in the collar and you come back to a half empty bottle sitting in a puddle of water. There is a ‘do not fill beyond this level’ mark on the side of the bottle to help avoid this but it is easy to overlook when you are tired or distracted.

I once cared for premature triplets that were on this type of bottle so had to clean 30 of them a day….which may go some way to explaining my aversion !

In some bottle designs you can hear or see a steady stream of tiny bubbles as the pressure equalises, which is very reassuring, but in other designs there is nothing to see or hear so you have to watch the way the baby is feeding to assess whether there is any equalising action. If baby is still frequently having to break the seal, or if the teat is collapsing under the vacuum, the simplest way to help is to very slightly unscrew the collar to allow air in. This works well, but do practise before trying to feed to find out at what point the bottle starts to leak (or flood !)


In returning to basics and going in to so much detail I am hoping that you will get to know every part of your baby’s bottles and understand why they work as they do.

This knowledge should go some way to easing the confusion that leads parents to discard perfectly good bottles or make unnecessary purchases.

It will also help you to buy the most appropriate bottle in the first place, and to realise that sometimes the best way forward is to stick with the bottles you have and give yourself and your baby time to adapt.

As I stated at the beginning of the article, this is based on bottles currently available in the UK so I would love to hear how useful those of you from other countries found it, and how your bottles differ from these ones. Any recommendations for great bottles along with your reasons for the preferences would, I am sure, also help fellow parents.

It is important to me that you feel you can trust me and my advice so I have made the decision not to officially align myself with any companies or brands.

I will very occasionally share my personal favourites with you, and the reasons why I like them but these will be tried and tested items, or new ones that really stand out in some way that I think will benefit you.

I will not be taking any payments or gifts from any companies or manufacturers, and any free samples I receive will be used as competition prizes for you, or redistributed to those in need

……..unless, of course, Lindt chocolate start making baby products then it is every man for himself !!!!!!! J xxx

The Author

I’m Sarah Norris, a Baby Care Consultant and Parenting Coach.

I have spent over twenty five years, often working 24 hours, 6 days a week, supporting hundreds of families with new or young babies aged from newborn to 12 months old, and often helping with their toddlers and older children.

I help parents discover what parenting style they want to use to care for their baby, and offer advice on different approaches that might suit them and their circumstances best.


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