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Woman wearing maternity bra

Getting the right pregnancy bra and, if you plan to breastfeed, nursing bra can be difficult. When might you start wearing one? What about fitting?

Bras and your changing breasts

During pregnancy your bump grows and most women notice that their breasts do too. For some women, the breasts start to get bigger as early as week six of pregnancy, while others say their breasts don’t start to grow until the third trimester (Healthline, 2017). The breasts increase in size because the hormones cause breast ducts to expand in readiness for breastfeeding (Alex et al, 2020).  

It's common to go up a cup size or two during pregnancy (Healthline, 2017). Many women notice they are also broader across the back because your rib cage expands to make room for your baby (NHS Start4Life, 2019).

A badly-fitted bra can cause poor posture, back pain and neck pain (Evans, 2019). That means wearing one that feels comfortable, supports your breasts and back, and which stretches to accommodate your growing breasts is very important at this time.

When to measure maternity bra size

It is recommended to have bras professionally fitted regularly and to change your bras every six months (Evans, 2019). This is particularly important during pregnancy when your breasts are changing. You might want to do this in the first trimester.

Some department stores and specialist shops offer a free measuring service and a range of maternity bras (Breast Cancer Care, 2019).

How to tell if a bra fits well

  • The entire breast should fit comfortably inside the bra cup, with no breast tissue bulging above or at the sides.
  • The centre front should sit flat against your body, regardless of the size of the breast.
  • The band around the bottom should lie horizontally across your back, be at the same level back and front and not arch when you move. When checked, you should be able to pull the band about an inch away from the body.   
  • The straps should not carry the weight of the breasts. They should sit on your shoulders without slipping or digging in. They can be adjusted to make sure they are comfortable.
  • If it is an underwired bra, the wire must sit flat against the body, around the breast, without gaping, digging in or pressing down on any breast tissue.
  • When buying a bra in pregnancy, it is best to buy one that does up comfortably on the tightest hook to allow room for further growth.

(Breast Cancer Care, 2019; Evans, 2019)

Some people buy maternity bras that double up as nursing bras as they have a clip which opens easily for breastfeeding afterwards.

Are nursing bras necessary?

If you are intending to breastfeed, you may want to think about buying some breastfeeding (or nursing) bras before your baby is born. As breasts tend to feel heavier during breastfeeding, most women find the support of a nursing bra makes them feel more comfortable. Some women choose to go bra-less or wear a cami or cropped top instead.

Nursing bras have drop-down cups, which are clipped to the straps and can be opened easily to expose the breast when feeding. To make life easier when you come to feeding, it is worth practising to make sure you can open the bra one-handed. That way, you’ll have got the hang of it before your baby arrives.

When to get a nursing bra fitted

It is best to be measured and have a nursing bra fitted a few weeks before your baby is born, especially if your breast shape is still changing towards the end of your pregnancy.   

When choosing a nursing bra, follow the tips above for being measured for a maternity bra. But be extra careful that the bra isn’t too tight and doesn't cut in on any area of the breast. A bra that is restrictive or too tight can cause blocked ducts, which can lead to mastitis (Australian Breastfeeding Association, 2017; Pearson-Glaze, 2019).

Wearing a sleeping bra

Some women find their breasts feel heavy and uncomfortable at night or they leak milk so need to wear breast pads. You might want to think about wearing a sleep bra, which would provide very light support. If your bra is too tight, it may lead to blocked ducts.

A lot of brands sell specific maternity sleep bras or you could use a cropped top instead (Australian Breastfeeding Association, 2017; Pearson-Glaze, 2019).

Mum of two Melissa said: “I bought lots of fairly inexpensive crop tops to wear under my pyjamas when I was pregnant. They were soft and not too restrictive but still gave me a bit of support at night.

“They were great after the birth of my daughter as well. I could also stick breast pads inside to help with leaks.

“And it meant I could save my proper nursing bras for the daytime so I wasn’t doing extra washing when I already seemed to be drowning in dirty laundry.”

Can you wear underwired bras when pregnant or breastfeeding?

You might have heard that underwired bras are not recommended in pregnancy. But as long as they are well fitted and size checked regularly, they should be ok (Breast Cancer Care, 2019).

When breastfeeding, the breasts can change in size between feeds, particularly in the earlier weeks. Fuller breasts can be slightly bigger and feel heavier just before a feed. Underwire can put pressure around the edges of the milk ducts, causing blockages.

If you're wearing an underwired bra, you need to be sure it is fitted extra carefully. Don’t wear one if it shows any signs of digging into the breast tissue (Pearson-Glaze, 2019). Some underwired breastfeeding bras have softer, more flexible wire, so they are less likely to cause a problem (Australian Breastfeeding Association, 2017).

Material gains

During pregnancy and breastfeeding, some women might experience itchiness, nipple sensitivity, tenderness or feel sweaty. That means choosing breathable fabrics for bras can help them feel more comfortable. Natural fibre fabrics like cotton and silk are more breathable than synthetics like polyester so they’ll help keep you cooler. See more tips on how to keep cool when you’re pregnant.

Underneath it all

When your body is changing, it’s well worth finding underwear that fits your new shape. Being comfortable and well supported can make a difference to how you feel.

Further information

Our support line offers practical and emotional support with feeding your baby and general enquiries for parents, members and volunteers: 0300 330 0700.

We also offer antenatal courses which are a great way to find out more about birth, labour and life with a new baby.

Article reviewed March 2022

Alex A, Bhandary E, McGuire KP. (2020) Anatomy and physiology of the breast during pregnancy and lactation. Adv Exp Med Biol. 1252:3-7. Available at:

Australian Breastfeeding Association. (2017) Choosing a maternity bra. Available at:… [Accessed 12th March 2022]

Breast Cancer Care. (2019) Breast changes during and after pregnancy. Available at:…? [Accessed 12th March 2022]

Evans. (2019) Is your bra harming your health? Available at: [Accessed 12th March 2022]

Healthline. (2017) Breast changes in pregnancy: what to expect. Available at: [Accessed 12th March 2022]

NHS Start4Life. (2019) Week 23 – your second trimester. Available at:… [Accessed 12th March 2022]

Pearson-Glaze P. (2019) Nursing bras FAQs. Available at: [Accessed 12th March 2022]

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