Flange fit is one of the smallest details that makes the biggest difference, and it is one of the first things I check when expressing is not working. If pumping hurts, or you are not collecting much, the flange is very often the reason. The flange is the funnel that sits over your nipple, and getting the size right makes an enormous difference to how comfortable pumping is and how much milk you express. This guide explains how to tell if your flange fits and how to get the right size.

Why flange fit matters so much

The flange draws your nipple into a tunnel as the pump works. If it is the wrong size, your nipple is either squeezed or over stretched, which hurts, can damage your nipple, and stops your breast draining well. A poorly draining breast makes less milk over time, so a badly fitting flange can quietly affect your supply as well as your comfort. A well fitting flange does the opposite, letting you pump comfortably and empty well.

Signs your flange is too small

  • Your nipple rubs against the sides of the tunnel as you pump.
  • Pumping is painful, or your nipple looks pinched or blanched afterwards.
  • Only part of your nipple is moving in the tunnel.
  • You have a sore ring at the base of your nipple.

Signs your flange is too big

  • A lot of your areola is pulled into the tunnel along with your nipple.
  • The areola rubs and feels sore.
  • Your nipple slides around and your breast does not drain well.

Signs your flange fits well

  • Your nipple moves freely in the tunnel without rubbing the sides.
  • Little or none of your areola is pulled in.
  • Pumping is comfortable, with no pain.
  • Your breast feels softer and drains well after a session.
  • Your nipple looks the same afterwards, not squashed or discoloured.

How to measure for the right size

Flanges are sized by the width of the tunnel in millimetres. You size to your nipple, not your areola.

  • Measure the width across your nipple at its base, in millimetres, not including the darker areola around it.
  • It is easiest just after a feed or a pump, when your nipple is drawn out.
  • Add a couple of millimetres to your measurement as a starting point, as your nipple needs a little room to move.
  • Measure both sides, as many people have a slightly different size on each breast and may need two different flanges.

Many pumps come with a large standard flange, often twenty four or twenty eight millimetres, and a great many people actually need a smaller one. Smaller flanges and inserts are widely available, so do not assume the size in the box is right for you.

Remember your nipples change

Your nipple size is not fixed. It can change in the early weeks after birth, when there is more swelling, and it can even swell a little during a pumping session. It is worth re measuring now and then, especially if pumping starts to feel different, and adjusting your flange or insert if you need to.

Setting up your pump well

  • Centre your nipple in the tunnel before you start.
  • Begin on a low suction and build up to a level that is strong but never painful. More suction is not better, and it will not empty you faster.
  • Warm your breast and do a little massage first to help your milk flow.
  • Massage and gently compress your breast while you pump, which is called hands on pumping and collects more milk.
  • A little nipple balm around the flange can ease any friction.
  • Stop when your flow slows and your breasts feel softer, rather than watching the bottle.

Pain is always a signal that something needs changing, usually the flange size or the suction. It is never something to push through.

Get help from your midwife, health visitor or an IBCLC if:

  • Pumping hurts, or your nipple looks pinched, blanched or sore afterwards.
  • You are pumping often but collecting very little.
  • You are not sure what flange size you need.
  • You are pumping to build or protect your supply and want a clear plan.

Call 999 or take your baby straight to A&E if your baby:

  • Is floppy or unresponsive
  • Will not wake for feeds
  • Is having trouble breathing, or their lips, tongue or gums look blue or grey
  • Has a sunken fontanelle
  • Is visibly jaundiced and unwell with it, for example floppy, hard to wake or not feeding. Yellowing shows most clearly in the whites of the eyes, the gums, and the palms and soles
  • Has dark urine or pale, chalky stools

How a consultation helps

Flange fit is one of those small details that changes everything, and it is much easier with someone to help. When I see you I can measure you, check your flange size and your pump setup, and make sure expressing is comfortable and actually getting the milk out, so it works for you rather than against you.