This is the first in a series that I have had percolating for a while: the stuff that women need to know about breastfeeding because no one else does. If maternal and infant health was really a priority and breastfeeding was really the norm, these posts wouldn’t be necessary because you’d either already know this stuff or wouldn’t need it to begin with. But neither is true (for now!), so settle in for a little anatomy lesson.

Back in July 2007, I attended a session by Dr. Peter Hartmann at the La Leche League International Conference in Chicago where he showed pictures of some groundbreaking research into the anatomy of the breast.

While the room watched in awe at the multi-coloured wax models of milk ducts and grainy video of ultrasounds, it was both amazing and confounding that he was presenting brand-new information about the basic structure of the breast.

What is more amazing to me is that more than 6 years after Dr. Hartmann and his colleagues originally published this new information in March 2005, the diagrams in both anatomy text books and reference materials available on-line have not changed.  The trouble with this is that this work was more than just fascinating to the lactation geek – they have significant implications for how to treat the breast in order to preserve lactation. Yet, the medical students today (who may never learn anything more than this about breast anatomy) are still learning an anatomical model that’s plain wrong.

Detail of the breast structure ©Medela AG, Switzerland, 2006

So, here’s what you need to know:

1.     You probably have fewer milk ducts.

The old model of the breast assumed that the average breast had 15 to 20 milk ducts that lead to the nipple. Hartmann’s research shows that the number is actually much lower: on average, between 9 and 10 with a very significant variation (from a low of 4 to a high 18 among mothers producing a full milk supply).

Who cares? Well, the fewer milk ducts you have, the more significant the severing of anyone of them is. If you have 18 ducts, then severing 2 of them isn’t likely to reduce milk supply much. If you have 4, then half of it is gone. It means that no one really knows how much an incision will affect a particular woman’s ability to produce milk. On the positive side, because they also start “branching” sooner into multiple ducts that end in the secretory lobules, incisions further back in the breast might compromise less (since the main duct can still collect from other branches if they are not cut).

2.     Your milk ducts are closer to the surface and the nipple base.

Textbooks suggest that the lobules of milk-making cells at the end of milk ducts where breastmilk is actually secreted are located quite far back in the breast near the chest wall and evenly distributed.

In fact, the milk ducts are quite a lot shorter and the secretory cells are much closer to the surface, within the first 3 cms. Furthermore, they are not neatly arranged in a radial pattern and may curl around each other in roundabout way on their way to the nipple.

Who cares? This research suggests that the closer to the chest wall you stay, the more likely you are to preserve milk-making ability – on the other hand, incisions that happen around the nipple (sometimes chosen because they are better hidden by the areola) are more likely to cause damage. Because the ducts are not evenly distributed, the effect of an incision is again going to be very individual – there may be several ducts or none at all at any particular location.

The idea of positioning a baby in a certain direction to clear plugged ducts? Not so likely to be helpful if your ducts take the scenic route – though nursing in different positions can still help.

3.     Your nipples aren’t fat.

Or they don’t sit on fatty tissue anyway – the tissue underlying the areola is almost all glandular. This means not only that an incision in this area is more likely to compromise lactation, but also that even fairly mild pressure at the wrong angle could block a duct and prevent milk ejection. Also, because the fat is not concentrated along the surface of the breast as was previously believed but is actually mixed throughout, removal of only fatty tissue is significantly harder.

Who cares? Well, partly it’s important because it means that a good latch is important to good milk transfer (duh), but also that gear like breast shells and pump flanges need to be even more carefully fitted to reduce ‘pinch points’ (no kidding).

4.     The lactiferous sinus does not exist.

Pretty much every text you read about breastfeeding refers to the “lactiferous sinus” – which refers to the widened ducts right behind the nipple where the milk is stored. The baby latches to the breast, compresses the sinuses and gets a hearty mouthful of delicious milk.

Except that apparently, the lactiferous sinus is the unicorn of anatomy – no matter how much good you think it does, it actually does not exist. The milk ducts do widen briefly when milk is ejected (letdown), but if the milk is not drained, the milk flows back up into the lobules that it came from.

Besides the small issue of technical accuracy, does it matter? Well, yes – though accuracy is reason enough. It points to a greater importance of the hormonal cascade that causes letdown – it’s not just the physical compression of the baby’s mouth that ejects the milk.

Are you so bored that you could cry by now? I was when I was stringing this all together. If you can only remember a couple things from all this, here they are:

1.     Keep incisions as far away from the nipple as you can. You are likely to sever fewer ducts with an incision toward the nipple than around it.

2.     No one can tell you with any certainty how much a particular incision will impair your milk-making ability – you may have 20 ducts all neatly arranged evenly or four that are completely assymterical. You won’t know until you try.

Note: This post is not medical advice. This is general information. Always consult a qualified medical practitioner and remember that many factors come into play when making a final recommendation for a particular breastfeeding dyad in a particular situation.