Mammary Constriction Syndrome

Mammary constriction syndrome (MCS) is a new explanation for deep breast pain during breastfeeding. It was first described by Edith Kernerman IBCLC and Eileen Park, IBCLC, ND.1

A tightening of blood vessels

If there is a sudden tightening (i.e. narrowing or constriction) of blood vessels in an area of the body, it reduces blood flow and oxygen to that area. This sudden tightening of vessels is known as vasospasm. If a baby breastfeeds in an uncomfortable or shallow latch (has mostly nipple in their mouth without plenty of breast tissue) this can trigger a nipple vasospasm which can cause a burning or stabbing pain in the nipple(s). And when a constriction of blood vessels happens deeper in the breast, it can cause deep stabbing or shooting pains in the chest—this collection of symptoms is known as mammary constriction syndrome.

Causes of mammary constriction syndrome

Tension in a mother’s shoulders or chest can cause her pectoral muscles beneath the glandular tissue in the breast to press on the blood vessels that supply the breast and nipples. Tension may have several causes including the way a mother is sitting to breastfeed for long periods or the tensing of her shoulders in anticipation of a very painful latch. Edith Kernerman explains;

Because of difficulties the mother may have had during pregnancy, labour, or after birth, she may have tightness in her shoulders and chest that causes her pectoral (chest) muscles to press on the blood vessels that lead to her breasts and nipples, causing a lack of blood flow and oxygen, leading to pain. This pain may be throbbing or constant, deep or superficial, itchy, tingling, aching or knife-like, burning or freezing, shooting, sharp or dull, or a combination of any of the above. Also, if a latch feels painful, the mother may tighten her shoulders, clench her teeth, etc., causing the cycle triggering pain to begin again.

Edith Kernerman recommends treating mammary constriction syndrome with a technique she calls pectoral muscle massage. This involves massage of the chest muscles to help ease the tension and trying gentle pectoral muscle stretching, just before a breastfeed. She also suggests a mother with this syndrome should try to keep her back supported rather than hunching forward over her baby and avoid carrying heavy items such as shopping bags or heavy car seats.

Pectoral muscle massage

Jack Newman is a Canadian paediatrician and breastfeeding author. There is a useful post online about mammary constriction syndrome on Jack Newman’s Community Facebook page. Here he describes how most cases of breast pain—and/or nipple pain—in breastfeeding mothers are the result of a poor latch at the breast. A poor latch can lead to the secondary problem of vasospasm symptoms of the nipple and mammary constriction syndrome (often mistakenly diagnosed as thrush on nipples as the symptoms are very similar). In the excerpt below Dr Newman briefly describes the treatment technique of pectoral muscle massage;

It involves rubbing the chest muscles (not the breast) quite vigorously for about 45-60 seconds on the affected side. There are four places to massage: 1) above the breast against the chest wall; 2) between her breasts just to the side of the breast bone; 3) under the breast against her rib cage; 4) on the side of her body, beside her breast, against the rib cage. One of these four areas is likely to be the ideal spot for her to relieve her pain.

baby on tummy, mammary constriction syndrome
Photo courtesy Emily Walker

Other causes of deep breast pain

Finding the causes of sore nipples or reasons for pain deep in the breast are not always straightforward—mammary constriction syndrome may only be part of the puzzle. Deep breast pain can be associated with engorgement with breast milk or mastitis and is sometimes confused with thrush. See our articles on Engorged Breasts, Mastitis Symptoms and Treatment and Thrush on Nipples for more information.

Seek skilled help

Contacting an International Board Certified Lactation Consultant (IBCLC) can help to find the most likely causes of pain and for more information see Causes of Sore Nipples and Why Does Breastfeeding Hurt?


Mammary constriction syndrome is a name given to symptoms of deep breast pain that can be caused by the constriction of blood vessels within the breast tissue. The pain is likely caused by a baby feeding in an uncomfortable latch and/or due to muscle tension either from the way a mother is sitting to breastfeed, or the tensing of muscles in anticipation of breastfeeding pain. Mammary constriction syndrome can be helped by a pectoral muscle massage and improving a baby’s positioning and attachment at the breast.