“IG what?!” is very often the response women get from healthcare professionals when they try to explain that Insufficient Glandular Tissue (IGT) might be the reason why they appear not to have a full milk supply. I don’t say this to disparage healthcare professionals, but to highlight the fact that relatively little is known about IGT (also sometimes referred to as mammary hypoplasia) and that women very often struggle to find doctors who know anything about the condition or are able to provide them with answers as to why they might have it. IGT is real though, has not been invented by South Dublin mums, and it is documented in the literature going as far back as 1958 when a study of 900 breastfeeding women found that 4% were unable to breastfeed due to insufficient glandular development (Deem, 1958b).

I have a particular interest in low milk supply. I’m currently doing research as part of an MSc. on women’s experiences of breastfeeding with primary low milk supply – finishing May 22 (hopefully!) and I plan to publish my research at some stage, watch this space. I see a lot of clients in private practice who have low milk supply and I estimate that around 90% of them have IGT. It’s not particularly rare. It is a thing, as they say, and the limited studies that do exist on it estimate a prevalence of around 5%, perhaps even a little higher. Please note: IGT often does not become apparent until 2 – 3 weeks postpartum when a baby fails to gain weight appropriately, so if you work in a hospital setting you might not see it.

As a lactation consultant I don’t diagnose IGT. I don’t diagnose anything – I leave that to doctors. However, when I see a client who presents with possible primary low milk supply, I do a full health history, assess a feed, look at the baby, assess the mother’s breasts (if she if happy for me to do so), and get as much detail as I can about the baby’s birth and the mother’s breastfeeding experience to date. Sometimes all of this points to IGT. It is often referred to as a “diagnosis of exclusion”, meaning all other causes of low milk supply should be excluded first, before determining that IGT is the most probable cause. There are certain characteristics that breasts lacking glandular tissue present with; wide spacing, bulbous areolae, asymmetry and a tubular shape (sort of long, not as round as your average breast). However, it can never be assumed that breasts that have some or all of these markers will not be able to produce a full milk supply. In my experience I find that most women with IGT will make somewhere between 50 and 90% of the milk their baby needs, which is fantastic! With skilled and sensitive help and the right kind of support, women with IGT CAN breastfeed! They just probably need to supplement their baby with some extra milk. How they do this is up to them. I present women with options – some opt to supplement using a bottle, while some prefer to supplement at the breast using any one of a number of devices (eg homemade SNS with PVC feeding tube, Medela SNS, Haakaa feeding tube or the Lactaid system). I plan to do another blog on at-the-breast-supplementation at some stage. I find that one of the big difficulties women with IGT face though, is lack of information, and unhelpful advice. Often they will have one person telling them to “just give formula” and that “some women can’t breastfeed” and another telling them “it’ll be grand, just keep feeding and doing skin-to-skin”, which suffice to say is NOT helpful to a mother who knows she cannot make enough milk to exclusively breastfeed. So, I started a low milk supply support group on Zoom last September to provide support to mums breastfeeding with low milk supply. It is on every second Monday. I wasn’t sure how it would work, but it’s working! I facilitate and provide some information and guidance, but for the most part the mums look after each other and I know that one of the biggest benefits people attending get is that they realise they are not alone.

Anyway, I’m getting sidetracked. The reason I actually decided to do this blog was to share some information about IGT, what is known and what isn’t. So here goes:

Insufficient glandular tissue (IGT), also commonly referred to as mammary or breast hypoplasia, is defined as insufficient glandular or milk-producing tissue to produce enough milk to support adequate infant growth and development (Neifert, Seacat and Jobe, 1985). The aetiology of IGT is not clear, but there are theories that it could be genetic or caused by oestrogenic environmental exposure in certain agricultural settings (Arbour and Kessler, 2013a). There is also some evidence that breast growth and development in utero and during puberty could be inhibited by androgens (Dimitrakakis and Bondy, 2009). Menstrual disorders such as delayed menarche or amenorrhea during puberty can inhibit normal breast development and result in IGT. Breast development also depends on tight regulation of zinc metabolism. Lee et al., (2015) discovered from their research on mice that loss of the zinc transporter ZnT2 resulted in mammary hypoplasia and failed lactogenesis II, but concluded that further research is required in human subjects. More recently, Kam, Bernhardt, Ingman et al., (2021a) conducted a systematic review of modern, exogeneous exposures associated with mammary gland development. They found that both an obesogenic diet and certain endocrine disrupting chemicals can alter mammary gland development and in turn impact future lactation capacity.

There are only a handful of case studies on breastfeeding with IGT in the literature (Arbour and Kessler, 2013a; Bodley and Powers, 1999; Neifert et al., 1985) and very little research has been done on the causes, diagnostic criteria or the prevalence of the condition. Huggins, Petol and Mireles (2000) conducted a study of thirty-four mothers with breasts suggestive of IGT and classified their breasts as type I, type II, type III or type IV using the Heimburg classification system (Heimburg, Exner, Kruft et al., 1996). They found that 61% of the participants were unable to produce a full milk supply within the first month. The study identified six physical characteristics of IGT which can be used in the antenatal period to identify women who may be at risk of insufficient milk production; lack of breast changes during pregnancy, breast shape, breast asymmetry, stretch marks on the breasts, a wide intramammary space, and areolar abnormalities. The authors highlighted the importance of emotional support for women with IGT who wish to breastfeed to help them work through feelings of anger, guilt, inadequacy and disappointment.

While the Heimburg classification system is useful in identifying IGT as a possible cause of primary low milk supply, it cannot be assumed that all women whose breasts are classified as type I, type II, type III or type IV will be unable to achieve a full milk supply. Lactation consultants in clinical practice often refer to IGT as a diagnosis of exclusion, meaning that all other possible causes of insufficient milk production such as hypothyroisism, polycystic ovarian syndrome or poor breastfeeding management should be ruled out before a diagnosis of IGT is made.

Although there is a glaring lack of research on IGT as it pertains to breastfeeding and lactation, it is well documented in plastic surgery literature on aesthetic breast surgery. These studies tend to focus on the appearance of the breast and the surgical techniques used rather than the underlying pathology. They use a number of different terms to describe breasts that lack glandular tissue or have an abnormal presentation, including breast hypertrophy, hypomastia (Neto, Neto, Abla et al., 2012), breast aplasia (Knackstedt, Deross and Moreira, 2020), tuberous/tubular breast (Zholtikov, Korableva and Lebedeva, 2018), developmental breast asymmetry (Chan, Mathur, Slade‐Sharman et al., 2011), the snoopy deformity (Gruber, Gruber, Jones et al., 1980), and congenital breast deformities/anomalies (Agbenorku, Agbenorku, Iddi et al., 2011).

Despite the dearth of studies on IGT, awareness of how it can impact milk supply and breastfeeding has grown among lactation consultants and mothers over the last decade, as evidenced by the number of IGT and low supply peer-support groups on social media and the number of lactation consultants informally blogging about it. There is currently a support group on Facebook called ‘IGT and Low Milk Support’ which has almost 10,000 members. In addition there was the publication of a book on the topic aimed at breastfeeding women who have IGT (Cassar-Uhl, 2014). However, much of what is known about strategies for breastfeeding with IGT is anecdotal and there remains a gap in the literature on studies on human subjects. According to Kam, Bernhardt, Ingman et al., (2021b), “further research is needed to investigate breast hypoplasia as one reason for a primary insufficient milk supply“.

Deem, H. M., H (1958b) ‘Breast-feeding’, New Zealand Medical Journal, 57, pp. 539-556.

Neifert, M. R., Seacat, J. M. and Jobe, W. E. (1985) ‘Lactation failure due to insufficient glandular development of the breast’, Pediatrics (Evanston), 76(5), pp. 823-828.

Arbour, M. W. and Kessler, J. L. (2013a) ‘Mammary Hypoplasia: Not Every Breast Can Produce Sufficient Milk’, Journal of midwifery & women’s health, 58(4), pp. 457-461.

Dimitrakakis, C. and Bondy, C. (2009) ‘Androgens and the breast’, Breast cancer research : BCR, 11(5), pp. 212-212.

Lee, S. et al. (2015) ‘Essential role for zinc transporter 2 (ZnT2)-mediated zinc transport in mammary gland development and function during lactation’, The Journal of biological chemistry, 290(21), pp. 13064-13078.

Kam, R. L. et al. (2021a) ‘Modern, exogenous exposures associated with altered mammary gland development: a systematic review’, Early human development, pp. 105342.

Kam, R. L., Cullinane, M. and Amir, L. H. (2021b) ‘Research Challenges and Considerations in Investigating Rare Exposures Using Breast Hypoplasia as an Example’, Journal of human lactation, pp. 8903344211037620-8903344211037620.

Neto, M. S. et al. (2012) ‘The Impact of Surgical Treatment on the Self-Esteem of Patients with Breast Hypertrophy, Hypomastia, or Breast Asymmetry’, Aesthetic plastic surgery, 36(1), pp. 223-225.

Knackstedt, R., Deross, A. and Moreira, A. (2020) ‘Congenital breast deformities: Anatomical basis and surgical approaches for optimal aesthetic outcomes’, The breast journal, 26(7), pp. 1302-1307.

Zholtikov, V., Korableva, N. and Lebedeva, J. (2018) ‘Tuberous Breast Deformity Correction: 12-year Experience’, Aesthetic plastic surgery, 43(1), pp. 16-26.

Chan, W. et al. (2011) ‘Developmental Breast Asymmetry’, The breast journal, 17(4), pp. 391-398.

Gruber, R. P. et al. (1980) ‘The “donut“ mastopexy: Indications and complications’, Plastic and reconstructive surgery (1963), 65(1), pp. 34-38.

Agbenorku, P. et al. (2011) ‘Awareness of Breast Developmental Anomalies: A Study in Jamasi, Ghana’, Aesthetic plastic surgery, 35(5), pp. 745-749.

Cassar-Uhl, D. (2014) Finding Sufficiency: Breastfeediung with Insufficient Glandular Tissue. Texas: Preclarus Press.