Nipple Shields Sizing : What You Need to Know Before Sending Your Partner to the Baby Shop

Thinking of using a nipple shield? You’re not alone. But when it comes to nipple shield sizing, there’s a lot more to consider than just the width of your nipple.

Nipple shields can be incredibly helpful—but they’re not as simple as picking a size and popping it on. They need to be fitted with care, used with guidance, and understood as a short-term tool—not a long-term fix.

 

Why Nipple Shield Sizing Isn’t One-Size-Fits-All

Many people think nipple shield sizing is as easy as measuring the diameter of the nipple and picking the corresponding size. But it’s not that straightforward.

Take this common scenario: A well-meaning partner is sent to the baby shop to pick up a nipple shield. They’re asked what size they need—and suddenly find themselves awkwardly trying to describe their partner’s nipples to a very patient retail assistant. (“Uhh… I think… medium?”) 😬

Needless to say, this usually doesn’t go well.

Because nipple shield sizing isn’t just about how your nipple looks at rest. During breastfeeding, the nipple stretches and expands—both in length and width. That expansion is essential, because your milk ducts need to dilate for efficient milk transfer.

Ultrasound imaging shows that women have anywhere from 4 to 18 milk ducts, with an average of around 9 per breast. That’s a huge range—and it helps explain why nipple shields need more than just a quick measurement to get right.

So no, nipple shield fitting isn’t as simple as measuring diameter. It’s about how your ducts and tissue respond to your baby’s intraoral vacuum during breastfeeding.

 

What This Means for Pumping, Too

The same principle applies to breast pump flange sizing. Many mums are told to pick a flange based on resting nipple diameter, but that doesn’t take into account tissue expansion, milk flow, or comfort. Just like nipple shields, flanges need a dynamic—not static—fit.

 

 

What to Consider When Choosing a Nipple Shield Size

Proper nipple shield sizing depends on:

• The functional nipple width during a feed (not just at rest)

• Efficient milk transfer, which can be impacted by too-tight shields

• The design of the shield—some are longer, wider, or have cut-outs

• And yes, some women need different sizes for each breast

 

 

Poor Sizing Can Create Problems

If your nipple shield is too small, you might notice:

• Nipple pain or friction

• Lower milk transfer (baby working harder for less milk)

• Reduced supply over time

A shield that’s too large may also cause issues with latch or seal. That’s why nipple shield sizing needs individualised support—ideally from an IBCLC who understands how babies feed, how shields affect milk flow and the biomechanics of breastfeeding.

 

 

Nipple Shields Come in Different Shapes and Sizes

A lot of mums actually need a larger size than they think. The right fit is based on your nipple’s functional diameter—not your baby’s mouth size.

Some shields include a cut-out section designed to sit under your baby’s nose. This helps keep their airway clear and allows them to smell your skin—something that helps trigger feeding reflexes. Double cut-outs can also improve chin-to-breast contact, another key factor for effective feeding.

 

What Does the Research Say About Milk Removal?

A 2020 study from UWA (Coentro et al.) found that even well-fitted nipple shields reduced milk removal by around 25% when compared to pumping without a shield.

They used a more accurate measure called PAMR (Percentage of Available Milk Removed) to see how effectively the breast was emptied. With the shield in place, it was significantly lower. This research doesn’t mean shields shouldn’t be used—but it does show they can impact drainage and, over time, may affect supply.

Also, babies don’t feed like breast pumps. The biomechanics are more complex and responsive. But this research still tells us something important: shields can affect drainage, and that might impact your supply over time.

So if you’re using one, it’s vital to have good support—someone who understands fit, flow, and when to recheck how things are going.

 

Nipple Shields May Soothe the Symptom—But Biomechanics Solve the Cause

Nipple pain is one of the most common reasons mums stop breastfeeding earlier than they hoped, so, understandably, people think nipple shields can be the answer to supporting breastfeeding journeys.

However, thanks to the work of Dr. Pam Douglas and others in the field of breastfeeding biomechanics, we now understand that most nipple pain isn’t about sensitive skin or anatomical problems—it’s about tension.

When your baby is poorly positioned or their body isn’t well-supported, it creates a breast tissue drag. This tension stretches and strains the nipple and areola, causing:

• Inflammation

• Micro-damage

• Friction wounds

• Pain with or after feeds

Sadly, this is often the point where nipple shields are reached for, alongside antifungals, antibiotics, tongue-tie releases, or even chiropractic work—often without anyone watching a full feed or helping with positioning.

 

There’s Good News

The two biggest factors in preventing and healing nipple pain are:

1. Eliminating mechanical tension during feeding (through refined positioning and eliminating breast tissue drag)

2. Avoiding overhydration of the skin (which can lead to moisture-related damage)

With the right support from someone who has an up-to-date understanding of the biomechanics of breastfeeding, many mums find that pain eases quickly—without needing a shield at all.

*For the academically minded, this is a great paper to read Rethinking Lactation-related Nipple Pain and Damage by Dr Pam Douglas

 

 

Fit and Hold Still Matter (Even With a Nipple Shield)

Using a nipple shield doesn’t mean latch and positioning stop being important. In fact, getting “fit and hold” right is just as essential when a shield is in place—if not more so.

If a baby is only drawing the nipple into their mouth and not taking in enough breast tissue behind it, they can end up nipple feeding, or continuing to create breast tissue, drag, which leads to:

• Inefficient milk transfer

• Ongoing nipple pain or trauma—even with the shield

• Frustration at the breast or frequent slipping off

Good fit and hold  ensure:

• The biomechanics of breastfeeding are working

• Baby uses their reflexes effectively

• Mum experiences less pain and better flow

So yes, even when using a shield, how you hold your baby and how they attach still matters. Sometimes, just a few simple changes in position can make a big difference to how effective and comfortable the feed is—for both of you.

 

Timing Matters

It’s usually best to avoid using a nipple shield before your milk comes in.

Why? Colostrum is produced in small amounts and is quite thick. A shield can make it harder for baby to transfer this early milk effectively. Once your milk is in and flowing, a shield may help—but only if it’s used with guidance.

 

Getting It On (Because Yes, It Can Be Fiddly)

Some mums are given tips such as:

• Stretch the rim outward before placing it

• Add breastmilk to help it stick

• Try to centre the nipple before folding the sides down

But what matters most is that your nipple is centred in the tip. Your baby’s intraoral vacuum will usually do the rest if you have good fit and hold.

 

Do Feeds Take Longer?

Sometimes, yes. Milk may flow a little slower through a shield, and that might be why feeds can take longer. But every baby is different.

 

Weaning Off the Shield

Some babies wean themselves off without a fuss. Others need a little support.

Here are a few gentle ideas:

• Start with the shield, then remove it mid-feed

• Offer the breast without the shield at the most dialled down feeds

• Try skin-to-skin and baby-led attachment

• Trust your baby’s timing—some just decide one day they’re done with it

If it’s not smooth, you’re not failing. You might just need a few tweaks and extra support.

 

A Quick Note on Flat or Inverted Nipples

Nipple shields aren’t only used for nipple pain—they’re often recommended for flat or inverted nipples too. But that doesn’t always mean they’re necessary.

When we understand the biomechanics of breastfeeding, we see that effective milk transfer relies more on a baby’s ability to latch deeply and use their reflexes well than on nipple shape alone.

So even with flat or inverted nipples, many babies can breastfeed effectively without a shield, especially with the right positioning and support.

You can read more about the fact it is all about creating a vacuum in my blog:

👉 Breastfeeding 101

 

Final Thoughts: It’s a Tool, Not a Fix-All

Nipple shields can be a useful short-term aid. But they don’t fix the root cause—and they do come with trade-offs.

If you’re using one, or thinking about it, make sure you’ve got evidence-based support behind you. I can help you:

• Decide if a shield is needed

• Find the right size and shape

• Monitor supply and flow

• Wean off when you’re ready

Because breastfeeding is more than milk—it’s a relationship. And you deserve care that supports both of you.

 

Need help with nipple shields, fit and hold, or supply?

Book a consultation with me. I offer evidence-based, judgment-free support to help you and your baby thrive—whatever your feeding journey looks like.