Insufficient glandular tissue

Why do my breasts look funny?

Some mothers have breasts that don’t develop properly. This is a condition called insufficient glandular tissue, or IGT. They don’t have enough milk tissue and as a result they don’t produce enough milk. The breasts may have unusual curves, be triangular or very long and narrow. Mothers with IGT can breastfeed but will generally have to supplement their babies with extra milk. Some mothers are encouraged to express after feeds and take medication, but neither is very effective in increasing their milk supply. If IGT is noticed before the baby is born, the baby should be monitored closely for the first few weeks after delivery to ensure the baby is getting enough milk. No one knows the cause of IGT and there is no treatment.

A) Describing IGT

Type 1 IGT.

The breast consists mostly of:

  • Fat cells
  • A supporting structure (ligaments)
  • Milk tissue (alveoli and milk ducts)

Some women’s breasts do not develop properly because they don’t have enough milk tissue. The problem becomes obvious during puberty, when the breasts do not grow as expected. The breasts will never make enough milk because of the reduced amount of tissue. The most common name for this is insufficient glandular tissue (IGT). It is also known as:

  • Mammary hypoplasia
  • Insufficient breast tissue
  • Tubular breasts

It is a frustrating condition because:

  • There is no treatment and no way to prevent it until we understand the cause.
  • It may not be recognized, so newborn babies may be extremely underfed.
  • Mothers with IGT are often encouraged to express after feeds and take medication to increase their milk supply. Neither is very effective, causing frustration, exhaustion, and possible medication side-effects.
  • Mothers wrongly believe they caused this problem.

B) Causes of IGT

The cause of IGT is not known (Osborne 2015). There may be genetic, hormonal, or environmental factors, acting individually or together (Guillette 2006; Lee 2016; Rudel 2011). 

Several chemicals (endocrine-disrupting chemicals) have been shown to affect the development and function of the breast and decrease the duration of breastfeeding (Criswell 2020).

Research has shown that obesity can impair the development of milk tissue.

The milk tissue of the breast develops a little with each menstrual period, so infrequent periods may contribute to IGT. 

C) Classifying IGT

Three types of insufficient glandular tissue.

There are several classification systems (Grolleau 1999; Wincour 2013). For the purpose of assessing breastfeeding, breasts affected by IGT fall into one of three types based on how they look:

  • Type 1: Tissue missing from the inside part of the breast. These breasts have a typical outward curve on the outside half, but the inside half is straight or bows in.
  • Type 2: Tissue missing from the whole breast, resulting in breasts that are very triangular and small.
  • Type 3: Tissue missing from the whole breast, resulting in breasts that are very long, narrow, and have an abnormally large areola. If any milk tissue is present, it is only found under the areola. This is also known as tubular breasts.

Images of each type of IGT are found at the end of this FAQ.

D) Diagnosing IGT

Wide spacing between breasts that is characteristic of insufficient glandular tissue.

Mothers with IGT can be affected to a greater or lesser degree meaning that their breasts may look closer to typical breasts or look very different. They may also have more or less milk.

1) Appearance:

Mothers with IGT have breasts that look different and often have trouble finding bras that fit. It is also common for the breasts to be quite different in size (Winocour 2013).

Women with IGT usually have breasts that are widely spaced, typically more than 4 centimetres (1½ inches).

2) During pregnancy

The breasts do not increase in size during pregnancy. If the mother is lighter skinned, few blue veins will be seen on the breasts. 

3) After birth

Breast filling on Day 3 or 4, when the milk comes in, is limited and will occur only where there is milk tissue. Mothers may notice:

  • No or minimal change.
  • Patchy filling with a few fuller lumps at various places in the breast.
  • Filling only under the areola.

When breastfeeding, the baby will show some or all of the signs of not taking in enough milk. The baby will only grow well when given milk supplements.

E) Breastfeeding with IGT

This baby’s mother had insufficient glandular tissue (type 1). As is common with otherwise healthy but underfed babies, this baby gained very quickly once supplements were started: 700 grams (24 oz) in seven days. He needed roughly 600 ml (20 oz) of infant formula supplements each day.

Mothers with IGT make a small amount of milk. Using before-feed and after-feed weights, we have found that mothers with severe IGT generally make less than 300 millilitres (10 U.S. fluid ounces) of milk per day by one month after delivery. Mothers with a full milk supply make about 800 ml (27 oz) per day between the first and sixth months.

If IGT is noticed before the baby is born, the baby should be monitored closely for the first few weeks after delivery to ensure the baby not underfed. 

With IGT, the problem lies with the amount of milk, not the quality. Babies of mothers with IGT require long-term milk supplementation. We encourage mothers in this situation to continue breastfeeding while supplementing.

Mothers with IGT face similar problems with each child, but they do tend to produce a little more milk with each baby.

A small number of mothers have breasts that appear to be affected by IGT but still have a normal milk supply (Huggins 2000).

F) Increasing milk supply with IGT

Mothers with IGT often try to increase their milk supply with medication and expressing. These are unlikely to be very effective.

The drugs domperidone and metoclopramide are sometimes prescribed. They work by increasing levels of prolactin, the hormone that starts milk production. These medications are generally not effective, because the problem is with the amount of milk tissue present and not the amount of prolactin.

Expressing in addition to breastfeeding to increase milk removal and stimulate the breast to make more milk is also not generally effective at increasing milk supply. If the baby is breastfeeding well, the breast is already properly stimulated and there is no point in expressing after feeds.

If a mother chooses to express after feeds to maximize her milk supply, this should only be done for the first few weeks after delivery. Milk supply is usually stable after four weeks, and expressing further will not cause any increase.

Expressing should be reserved for a situation in which the mother and baby are separated or the baby is not breastfeeding effectively.


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