This episode is your complete guide to bottle feeding. Learn how bottle sizes and nipple flows work and how to choose the right bottles for your baby. Explore safe ways to warm milk and simple and effective routines for cleaning and sterilizing. Get practical tips to make feeding easier, reduce gas and spit-up, and avoid common pitfalls. Plus, if you are still breastfeeding, learn how you can introduce a bottle without disrupting your breastfeeding relationship.

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Article and Resources

I support the decisions you make for you and your baby when it comes to feeding. My goal is to provide accurate, evidence-based information and support to help you succeed. You can find all of the breastfeeding resources, episodes, and articles here.

Breastfeeding and Bottle Feeding

Breastfeeding is not mutually exclusive of bottle feeding or infant formula. You need a bottle to feed your baby pumped breastmilk. Introducing or supplementing with formula does not mean you have to stop breastfeeding; the two can work together. Plus, you always have the option to stop breastfeeding and exclusively bottle-feed your baby infant formula.

By six months, 3 out of 4 babies receive infant formula in a bottle. Only about 8% of babies never use a bottle, which means roughly 92% will take breast milk or formula from a bottle at some point in the first year. Although bottle feeding seems straightforward, it can feel awkward at first while you and your baby get the hang of it. Whether you are exclusively breastfeeding and occasionally offer a bottle of expressed milk or you wean and use formula exclusively, the vast majority of babies will be bottle-fed at some point.

Types of Bottles

You have a lot of options for types of bottles. They vary in size, shape, and material, and they have pros and cons. Generally, bottles and nipples come in a set, and if you try to combine one brand of nipple with another brand of bottle, you may find they don’t fit together correctly. Some babies prefer one bottle over another, so you may have to try several before finding one your baby likes.

Plastic Bottles

Bottles are made primarily from plastic. These are inexpensive, lightweight, and will not break if you drop them. They also don’t sweat or form condensation. Although plastic looks very smooth, it has tiny indentations and can be scratched easily, making it a bit harder to clean, and bacteria can hide in those scratches and indentations. Plastic does tend to wear down over time, especially with exposure to heat.

BPA

BPA (bisphenol A) is an industrial chemical most commonly found in plastics. Exposure to BPA is a concern because it is a hormone disruptor. BPA is a xenoestrogen, which means that it mimics estrogen. Specifically, it mimics estradiol, which is the strongest of the four main types of estrogen hormones in your body.

The good news is that the FDA banned BPA in baby bottles, sippy cups, and infant formula packaging over a decade ago. The bad news is that there are questions about whether the chemicals replacing BPA are genuinely better. The two primary replacement chemicals for BPA are BPF and BPS. Both of these have a similar chemical structure to BPA, and there have been concerns that these replacements are not safe alternatives; they are less well-studied, and there is less information available on their safety.

There is evidence that infants exposed to analogues of BPA, like BPF or BPS, during pregnancy and lactation can result in fetal growth restrictions, neurological dysfunctions, and metabolic disorders with the potential to persist throughout childhood. One study looked at the effects of BPF and BPS on testosterone secretion. They found that these alternatives impacted testosterone secretion at least as much, and in some cases more than BPA.

The bottom line is that we do not know that products labeled as BPA-free are safe because they could contain BPF or BPS. We do not know enough about these chemicals to know whether they are safe on their own or safer than BPA.

Microplastics

Another concern with using plastic baby bottles is microplastics. These are tiny fragments of plastic, ranging from microscopic to small but visible. Plastic particles are released over time as a product is used, especially when it is worn down.

There is evidence that microplastics can cause changes in the digestive, reproductive, central nervous, immune, and circulatory systems of a child. A study investigated the potential exposure of infants to microplastics from consuming formula prepared in polypropylene infant feeding bottles. (Polypropylene is the most common material for plastic bottles.) Researchers found these bottles release microplastics with values as high as 16,200,000 particles per liter. They also found that sterilization, exposure to high temperatures, and mechanical friction, like shaking a baby bottle to mix formula, can significantly increase microplastic release. Unfortunately, microplastics are impossible to avoid altogether. They are found in our water, food, and even the air we breathe.

In 2024, class action lawsuits were filed against several baby bottle manufacturers, including Dr. Brown, Nuk, Philips Avent, and Tommee Tippee. The lawsuit claims the companies failed to properly warn caregivers and parents that their bottles and baby cups allegedly seep harmful chemicals into food when heated. These lawsuits are still ongoing. Interestingly, nearly all baby bottle manufacturers now have glass, silicone, or other options available, and years ago, there were very few brands that offered alternatives to plastic.

If this all sounds concerning, remember that your baby only needs to use a bottle for about the first year. This is not something they will use forever. We will also explore alternatives to plastic and techniques to reduce BPA and microplastic exposure if you do use plastic bottles.

Silicone Bottles

Silicone is a synthetic material made from silicon, oxygen, carbon, and hydrogen. This material is flexible, durable, and temperature-resistant. Silicone does not have the risks of chemicals or microplastics that plastic bottles have. This material is also soft to the touch, and it is thought that some babies find it comforting. One downside is that it is more expensive than plastic.

Glass Bottles

There are two primary benefits to using glass bottles. One is that glass does not have any of the risks of chemicals or microplastics associated with plastic. The other is that, unlike plastic, glass has an entirely smooth surface, making it easier to clean. There are also downsides to using glass. There is always the risk that the glass breaks. Often, glass bottles are used with a silicone sleeve to help cushion the bottle and prevent breakage if dropped, or help contain the glass if it breaks. Some bottles are sold with a silicone sleeve, or this may be an additional purchase. This leads to the next downside, which is that glass bottles are more expensive than plastic. Lastly, some daycares will not allow glass bottles for liability reasons.

Stainless Steel Bottles

Another alternative is stainless steel. Stainless steel is more durable than plastic or glass and is easy to clean. The downsides are that this material is not transparent, measuring how much milk is in the bottle can be challenging, and stainless steel is more expensive than glass, silicone, and plastic bottles.

Size, Shape, and Design

In addition to the different materials, baby bottles come in various sizes, shapes, and designs.

Bottle Sizes

Bottles typically come in two basic sizes. Infant bottles generally are 4 or 5 ounces (120-150 ml). For older babies, the bottles are around 8 or 9 ounces (240-270 ml). You may also find some brands in 7 ounces (200 ml) and 11 ounces (330 ml).

Standard Bottles

Standard bottles have straight or slightly curved sides and are likely what you picture when thinking of a classic bottle. Some bottles have a more contoured or hourglass shape than others. The pros of the standard baby bottle are that they are easy to fill and hold, and simple to clean. Standard bottles are also compatible with most breast pumps and bottle warmers.

Wide Bottles

Wide bottles are shorter and wider than a standard bottle. The idea is that wide-neck bottles and wide nipples feel more breast-like to babies, which may make switching between breastfeeding and bottle-feeding easier. These bottles can be more expensive than standard bottles, and sometimes they do not fit in all warmers or diaper bag bottle pockets.

Anti-Colic Bottles

Anti-colic bottles are designed to reduce the amount of air your baby swallows. The goal is that this prevents gas, spit-up, and colic symptoms. Different brands use different venting systems to accomplish this. Some have simple one-piece vents built into the nipple or collar, while others use more complex inserts. One common style is the natural-flow bottle, which uses a straw-like vent system in the center of the bottle. This eliminates the vacuum that can form when a baby sucks, so no air bubbles mix with the milk. These bottles may help reduce the amount of air your baby takes in, though evidence is mixed. Downsides are that they often cost more and may have extra parts to wash.

Bottle with Disposable Liners

Bottles with disposable liners feature a bottle and nipple, but the milk or formula goes into a plastic bag that fits inside the bottle. The liners are marketed as presterilized and collapse as your baby drinks, which may minimize air intake. The trade-off is that you need to continually buy new liners, which increases costs, and the plastic bags are less environmentally friendly compared to reusable bottles.

Angle-Neck Bottles

Angle-neck bottles have a bend at the neck and have become less common over the years as new designs have emerged. Milk collects at the nipple end of the bottle, which manufacturers claim makes babies less likely to swallow air. This shape may also work well when feeding your baby in a more upright position.

Bottle Nipples

Just as bottles vary, nipples do too in their material, shape, and flow rate.

Nipple Materials

Baby bottle nipples are either latex or silicone. Latex nipples are soft, flexible rubber that are typically light brown or yellow. They are inexpensive and may feel more like a natural nipple, but many babies are allergic or sensitive to latex, so parents often avoid them. Silicone nipples, on the other hand, are clear, firmer, and more durable. They do not absorb odors or flavors, are extremely unlikely to cause an allergic reaction, and are the most common type of nipple used today.

Nipple Flows

Bottle nipples come in different flows designed to control how quickly milk comes out. The flows are: newborn, slow, medium, fast, or stages: 1, 2, 3, or 4. While manufacturers list age ranges along with the flow or stage, these are only guidelines. If your baby is getting too much milk too quickly and choking or sputtering, you may need to go with a slower-flow nipple. On the other hand, if they get frustrated and do not get milk out fast enough, you may need to graduate to a faster flow.

Nipple Shapes

Nipples come in many different shapes and sizes. The most common nipple is a simple round nipple. They also have orthodontic nipples, which tend to be flat on one side. Wide-mouth bottles tend to have a wider nipple. When you compare different types of nipples, you will see some shorter than others, and some moms find it helpful to find a nipple similar to their own. This can be particularly helpful when you are combining breastfeeding and bottle feeding.

Finding the Right Bottle and Nipple

Some studies compare different types of bottles, especially those marketed for mimicking the breast, anti-colic, or other benefits. Unfortunately, there is limited evidence. Plus, most of the research is funded by bottle manufacturers. (Like this study funded by Phillips AVENT or this study funded by NUK), which has the potential for bias. There is no strong independent research proving that one bottle type is superior. The reality is that all babies are different and may prefer different bottles and nipples. You may need to try several before finding one your baby likes.

Resist the urge to stock up on bottles before your baby arrives. If you create a baby registry, consider adding a few starter kits from various brands to try out different products. Once your baby settles on a bottle they like, you can invest in more of that brand. If a friend has a bottle you are curious about, you can borrow one to test before purchasing. If you borrow a bottle to test it out, you can easily sterilize it before and after use. Ultimately, the best bottle is the one your baby drinks from, and that may take some trial and error.

When to Introduce a Bottle

The “right” time to introduce your baby to a bottle depends on your situation. If you need to use a bottle out of necessity for medical reasons or because you are returning to work, introduce it whenever you need to.

If you have the luxury of waiting, aim to establish breastfeeding first and introduce a bottle around 3–4 weeks, and ideally by 5–6 weeks. This window helps protect breastfeeding while avoiding a late introduction that some babies may resist. Your baby has to work harder to get milk from breastfeeding than they do to get milk out of a bottle. Since bottles are easier for babies, some mothers end up in a situation where their baby prefers a bottle over breastfeeding because it is easier. On the opposite end of the spectrum is the fear that if you wait too long, your baby may refuse a bottle because it is not your breast. This can be particularly stressful for mothers returning to work after maternity leave.

Do not wait until your first day back at work to bottle feed your baby. Start 1–2 weeks beforehand so your baby can practice with another caregiver. Ultimately, you will need to decide when the right time is, and depending on your circumstances, that may not be in your control.

Mixing Infant Formula

If you use infant formula, always follow the water-to-formula ratio instructions on the label. Never water down formula more than directed, since too much water can cause water intoxication in babies. For powdered formula, use only the scoop that comes with that particular container. Different brands may have slightly different scoop sizes.

Although there is bottled water marketed specifically for mixing formula, this is not necessary. As long as your tap water is safe to drink, it is safe to use for formula. The American Academy of Pediatrics has criticized the mixed messaging on formula packaging about boiling water and then letting it cool. If you are unsure about your tap water, you always have the option to use filtered or bottled water. For premature babies or babies with health concerns, ask your pediatrician whether you need to be more stringent about your water source.

Baby Formula Maker Machines

There are countertop devices that hold powdered formula and water, then dispense a mixed, warmed bottle at the push of a button. It is essentially a Keurig or Nespresso machine for baby bottles. Some models even offer wi-fi/Bluetooth connectivity so that you can make a bottle from an app on your phone.

The most recognized brand in Baby Brezza. In the marketing for the Baby Brezza, they note that it is more accurate, consistent, hygienic, and faster than hand scooping. The group that manufactures the Baby Brezza actually funded a study that found 1/3 of all bottles made by hand were inaccurate by 10% or more. The same researchers even did a study to investigate whether a crying baby increased the margin of error. While there was still some margin of error, a crying baby had no effect. Consumer Reports evaluated two Baby Brezza models and one Baby Exo unit and found inconsistent formula-to-water ratios and fluctuating bottle temperatures across all three.

Anecdotally, I have heard great reviews from parents, and these devices have relatively good online reviews. While these offer convenience, you do need to refill water and formula and periodically clean the machine. It is also a good idea to monitor the formula-to-water ratios it makes and ensure the formula is at a safe temperature before giving it to your baby.

Warming Breast Milk or Formula

Some babies will happily drink milk or formula cold or at room temperature. Try this first, and you may get lucky and not need to warm bottles at all. If your baby prefers it warmer, remember that breast milk comes out at body temperature. The goal is to heat the milk or formula slightly, not to make it hot.

Never microwave bottles, as microwaving can create dangerous hot spots. Plus, microwaves can break down some of the nutrients in breast milk. Instead, you can use a baby bottle warmer or place the bottle in a cup or bowl of hot water for a few minutes. If you are warming frozen breastmilk, you can thaw it in the fridge, run it under warm water, or place it in warm water. With time, you will learn the right temperature of water to use and how long it takes for the milk or formula to reach the right temperature. Since babies are more sensitive to temperature than adults, always test the bottle before feeding by placing a few drops on the inside of your wrist. It should feel warm, not hot.

Cleaning

You can handwash bottles and nipples with a gentle dish soap and warm water, and air-dry them. A small dedicated bottle drying rack to place all of the parts is very handy. You also have the option to run parts and bottles through the dishwasher. A small dishwasher basket is helpful to keep small parts contained.

Sterilizing

It is a general practice to sterilize bottles and nipples before you use them for the very first time. Some parents make it a habit of sterilizing them periodically, but it is typically not necessary before each use. If you plan to use a dishwasher, the dishwasher’s high temperature will sanitize the parts, and many models have a dedicated sterilize setting. If you handwash parts, there are electric steamers that will sterilize bottles, microwave steam sterilizers, and sterilizers that use UV light. Plus, you can always place parts in a pot of boiling water for 10 minutes to sterilize them. For healthy babies, some parents decide this is not necessary and skip sterilizing altogether. If you have questions about sterilization, talk to your pediatrician. They may recommend that you sterilize bottles more frequently if your baby is born prematurely or has health considerations.

Minimizing the Risks of Heat on Plastics

One consideration for your method of cleaning or sterilization is that heat breaks down plastics. Products labeled “BPA-free” may still leach endocrine-disrupting chemicals like BPS or BPF when heated. Plus, there is evidence that exposure to high temperatures can significantly increase microplastic release. You can limit the exposure to heat by hand washing rather than using a dishwasher. Or if you choose to use a dishwasher, you may consider removing them to air dry rather than running through a heated dry cycle. The only method of sterilization that does not use heat is UV light.

Bottle Feeding

Feeding your baby a bottle may feel a little awkward at first, but with time, both of you will get the hang of it. One of the great benefits of bottle feeding is that other people can help feed your baby. For partners, feeding your baby is a fantastic opportunity to bond, build closeness, and share in caring for your little one.

Positioning Your Baby

To get your baby comfortable, support their head in the crook of your arm and hold them at about a 45-degree angle. Because holding a baby for a while can get tiring, you may want to use a pillow under your arm for extra support. Nursing and feeding pillows, like this one, can be especially helpful for new parents to make you and your baby more comfortable during both breastfeeding and bottle feeding.

As you feed your baby a bottle, they should sit or lie so that their head is higher than their stomach. Avoid letting your baby drink from a bottle while lying flat. This position can allow milk to flow into their Eustachian tubes and pool behind the eardrum, which raises the risk of ear infections. It also helps to switch the side you hold your baby on from time to time to support healthy muscle development, keep your arm from getting tired, and prevent your baby from favoring one side.

Bottle Position and Latch

Hold the bottle at an angle so that milk fills the nipple. This position will help prevent your baby from swallowing extra air. Your baby’s latch on a bottle is similar to their latch at the breast. Most of the nipple should be in their mouth, and their lips should flare outward. Many parents call this the “duck lips” look, which is a sign of a good latch.

Your baby will let you know when they have had enough milk or formula. Signs include turning their head away, slowing their sucking, or pushing the nipple out with their tongue. When you are done feeding your baby, keep them upright for a little while rather than lying them flat right away. This can help reduce spitting up and make it easier to burp them if needed.

Burping

It is a good habit to burp your baby during and after feedings. Aim to burp them about halfway through a bottle. This is also an excellent opportunity to switch sides. Then burp them again at the end of a feeding. If your baby tends to swallow a lot of air, you may need to burp them more frequently. This helps your baby stay more comfortable, minimizes spitting up, and can reduce gas by releasing air before it travels through the intestinal tract.

You can burp your baby by holding them upright over your shoulder, sitting them on your lap while supporting their chest and head, or laying them across your lap on their tummy. Whichever position you choose, gentle pats or rubs on their back usually do the trick.

Combining Breastfeeding and Bottle Feeding

Introducing a bottle to a baby can be stressful, especially if you intend to continue breastfeeding. You want your baby to be comfortable drinking from a bottle. However, you don’t want them to prefer that method over breastfeeding. You may have heard the term “nipple confusion”. This describes a baby’s fussiness or frustration when they have issues switching between a bottle nipple and a breast. This is one of the reasons breastfeeding resources recommend establishing breastfeeding before introducing a bottle, and to introduce a bottle during the window between 3 and 6 weeks.

Some tips can make breastfeeding and bottle feeding work well together. First, let your baby control when the feeding begins. You can do this by allowing them to draw the nipple into the mouth rather than you pushing the nipple into their mouth. You may also stroke your baby’s lips from top to bottom with the nipple to elicit a rooting response and open their mouth wide to accept the nipple rather than poking it in.

Next, let your baby decide when they are done. Generally, you wouldn’t encourage them to finish the last bit of milk in the bottle by forcing the nipple into the mouth, massaging their jaw or throat, or moving the nipple around in their mouth. If your baby is falling asleep and releasing the bottle nipple before the bottle is empty, that is okay. Think about how you would handle a similar situation if you were breastfeeding. You likely wouldn’t be waking your baby up, trying to get them to drink more milk every time they fall asleep at your breast.

Paced Feeding vs. Responsive Feeding

The advice for bottle feeding a breastfed infant from many resources has long been to practice paced feeding. Paced feeding involves the baby sitting more upright, using a slow-flow nipple, holding the bottle more horizontally, and building in pauses. The idea is that this mimics the breastfeeding mother’s let-down patterns and discourages drinking the bottle too fast. There has been some criticism of paced feeding. More recently, the American Academy of Pediatrics has shifted toward advising responsive feeding. This generally follows your baby’s cues for when they are hungry or full and not forcing pauses or breaks during feeding. The concern is that paced feeding does not allow a baby to practice self-regulation of their nutritional intake and recognize their satiety cues, and could result in underfeeding babies.

I went down a rabbit hole looking into the research on this, and the results are mixed. Most of the research regarding responsive feeding is with solid foods, rather than bottles. Responsive feeding discourages restricted feeding. Some sources consider the act of building in pauses with paced feeding as restricting feeding. All of the resources that recommend paced feeding also recommend many aspects of responsive feeding and following your baby’s cues. A practical middle ground is to keep feeding responsive by watching for hunger and fullness cues. If you feel like your baby is drinking too fast and is gulping or coughing, you may want to build in some pauses. With time, you and your baby will find a rhythm that works.

Lactation Consultant

If you run into any difficulties with bottle feeding, a lactation consultant can be an excellent resource. Although lactation consultants primarily work with breastfeeding mothers, they are experts in observing infant feeding behavior. They can watch a feed and help you identify any issues, such as if the flow is too fast or too slow, if there is a nipple shape mismatch, air intake, or positioning issues. Consultants can also troubleshoot common problems like bottle refusal, frequent spit-ups, gassiness, or very long or short feeds, and they can help you coordinate pumping and bottle schedules so your milk supply stays where you want it. Many work in pediatric practices, hospitals, or via telehealth, and some services are covered by insurance.

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