Breast pump shields

How do I choose the right size of breast shield?

It’s important to get the right size of breast shield. The shield should allow the nipple to move forward and backward without pain and allow only a small portion of the areola and nipple root into the tube that covers the nipple. That tube, or barrel, is commonly 24 millimetres wide. Other sizes are 21, 24, 27, 30, and 36 mm. If mothers have the correct size, they should feel no pain, get the expected amount of milk, and pump each breast in no more than 20 minutes. If it’s too large, the nipple root and milk ducts may be stretched too much, causing pain and swelling. If it’s too small, the mothers' nipples may be injured by scraping along the sides of the barrel. In both situations, the milk flow can be poor. To find the right breast shield, mothers may have to try different sizes. Shield size may also change over time. 

A) Describing breast shields

Breast shields have a cone-shaped part (the funnel) that touches the breast and areola, and a narrower tube (the barrel) for the nipple and a small part of the areola.

Breast shields are very different from nipple shields.

Specific information about breast shield design and sizing can be found on the websites of individual pump companies.

B) Choosing a breast shield size

Breast shields vary in size. They are measured by the width of the barrel opening. Most pumps supply 24-millimetre breast shields, but other sizes are usually available. Common sizes are 21-mm, 24-mm, 27-mm, 30-mm, and 36-mm.

It is very important to have the correct size of shield to allow the nipple to move forward and backward in the shield without pain and to allow only a small portion of the areola and tissue underneath (the nipple root) into the barrel.

While most mothers find the 24-mm size effective, others may need to use a different size. The size can also change with time (Jones 2009). A small number of mothers may need a different breast shield size for each nipple.

1) Correct breast shield size

Mothers can estimate the best shield size by measuring the width of the nipple where it meets the areola (the nipple bottom). Choose the shield size that is closest to the size of the nipple bottom and is at least two millimeters wider than the nipple bottom.

If your breast shield size is correct, you should expect:

  • No nipple pain or damage.
  • To obtain the expected amounts of milk.
  • Pumping one breast to take a maximum of 20 minutes.
  • For the breast to feel completely softened after pumping.

2) Breast shields that are too large

If the breast shield is too big, the nipple travels too far down the barrel, which can result in pain and reduced milk flow from:

  • Excessive stretching of the nipple root.
  • Excessive stretching of the milk ducts inside the nipple root.
  • Swelling of the nipple root.

Noise can be a sign that the shield is too big and is losing suction, allowing air to enter.

3) Breast shields that are too small

If the breast shield is too narrow, the nipple scrapes along the sides of the barrel. You may notice dead skin in the barrel. If it is much too small, the nipple may not even be able to enter the barrel.

Breast shields that are too small can cause:

  • Pain and injury to the nipple sides and bottom.
  • Swelling of the nipple.
  • Poor milk flow.

C) Breast shield style

The part of the funnel that touches your breast and areola may be hard or it may be padded with a soft, flexible surface. It may even have ridges and bumps. There is little information on which type is the most effective. 

The angle of the funnel and the funnel can vary and may affect the amount of milk removed from the breast (Sakalidis 2020).

D) Breast shield inserts

Breast shield inserts can be used to modify a shield. There are a number of commercial inserts available and the effect depends on which insert is chosen. They may:

  • Increase or decrease the shield size.
  • Add padding to the shield funnel.
  • Change the angle between the shield funnel and the barrel.


Jones E, Hilton S. Correctly fitting breast shields are the key to lactation success for pump dependent mothers following preterm delivery. J Neonatal Nursing 2009;15(1):14-17

Sakalidis VS, Ivarsson L, Haynes AG, et al. Breast shield design impacts milk removal dynamics during pumping: a randomised controlled non-inferiority trial [published online ahead of print, 2020 May 13]. Acta Obstet Gynecol Scand. 2020;10.1111/aogs.13897