Choosing the right breast pump comes down to sizing. More specifically, the size of your pump’s flanges.

A flange is an essential part of your breast pump kit. It fits right over your nipple and creates a seal, connecting your breast to the actual pump so you can extract milk. Whether you have a wearable, hands-free pump or a plug-in pump, every single pump type will have flanges.

If the flange doesn’t fit correctly, it can cause discomfort, lead to milk blockages, and reduce milk production. Luckily, you can avoid these problems with a few sizing guidelines.

Whether you go hospital-grade or wearable for your new breast pump, nothing will be more important than having the correct flange size.

If your flanges are too small, your nipples will run up against the sides of the flange. Now imagine that rubbing happening multiple times a day over a year. This constant irritation can lead to nipple soreness, pain and even infection.

A flange that’s too big comes with its own set of problems. It can cover too much of your areola and breast tissue, which causes major discomfort.

In both cases, there’s an even more pressing issue: milk expression. Whether it’s too small or too big, the wrong flange size won’t extract your breast milk efficiently. This can lead to breast milk reduction and clogged milk ducts, which often manifest as a tender lump in your breast.

You can avoid these painful symptoms by picking the right flange size.

Breast pumps come in various sizes, and it can be hard to know which one will fit you comfortably. While there are average-sized pumps, you’re not guaranteed they’ll be right for you. Your body is unique, so it’s best to use a helpful size guide and take accurate measurements.

The first step is to measure the widest part of each nipple with a measuring tape. Keep in mind that your measurement should be of your nipple’s diameter only, not your areola. Start at the base of the nipple and measure to where it meets the areola.

Once you have your measurements, compare each nipple’s diameter to the manufacturer’s size guide. The guide will show you which flange size corresponds with the size of your nipple.

It’s not always easy finding a pair of jeans or a bra that fits perfectly, and the same goes for breast pump flanges. Size guides and taking measurements will help you narrow down which flange size is right for you, but ultimately you’ll have to test the flange yourself.

The primary thing to look for is whether your nipple is centered in the flange and the tunnel. It should move in and out of the flange’s tunnel, imitating the way your baby sucks on your nipple.

Your nipple shouldn’t rub up against any of the tunnel’s sides. If it does, the flange may be too small. Little or no areola tissue should be pulled into the tunnel when the breast pump is working. If your areola tissue is being pulled, the flange may be too big.

Pumping for the first time will always feel a little strange. But if you experience any pain, discomfort, irritation or soreness, that’s a sign you have the wrong flange size. If your milk extraction is low and your breasts still feel full after pumping, that can also indicate you need to try a different size.

Related Reading: A Guide to Finding Your Willow Flange Size

If you’re struggling to find the right size flange or are stuck debating which flange size to try first, you aren’t alone. Instead of remeasuring and analyzing each option, try reaching out for support.

If you haven’t gotten a breast pump yet, try talking to other moms. Whether it’s through a friend, a relative or an online group, go ahead and ask for advice. Breastfeeding moms are a special, supportive community who can offer guidance and insights that you often can’t get anywhere else. If you’ve tried out a few flange sizes and are still struggling, consider reaching out to a lactation consultant. You can connect with the hospital where you gave birth or ask your community for a referral. A lactation consultant can help you find the right flange size and troubleshoot any other issues you may have as well.

Finding the right flange size can be frustrating, but it’s the best way to ensure a comfortable pumping experience. Whether you’re researching flange sizes for the first time or feel like you’ve tried every size under the sun, Willow is here to help. At any time, you can reach out to our Mom Squad for help with your wearable pump. From troubleshooting size issues to offering you encouragement, we’ll help you take positive steps forward so you can fully enjoy nursing your baby.