Why is my breast milk clumpy?- Ask an LC

" Dear Shondra,

A couple of days ago, I noticed a slimy substance (pic below, left) hanging in my pump. Upon further inspection, I noticed a huge piece in my milk, which shrunk as I moved it around. Since then, every time I pump my right breast, the milk from that breast gets clumpy while sitting in the bottle (pic below, right). Why is my breast milk clumpy? Is this fat or something else?"

Clumpy breast milk is often very perplexing to parents, especially when the clumps develop soon after pumping. From the pictures that you've provided, and based on the information you've shared, it sounds like the clumpy milk may be due to a case of subclinical mastitis.

Other descriptors for clumpy milk may include Slimy, thick and gooey, stringy, globs, mucusy. lumpy,

Though mastitis is a term that, by definition, means breast inflammation, in some cases, mastitis can be caused by an infection. If your clumpy breastmilk is, in fact, due to subclinical mastitis, it means that you have mastitis from a breast infection without having any symptoms of it.

It is possible the "milk plugs" -the milk that was hanging in your pump on the first day- developed as a result of the infection. It's also possible, though less likely, the infection in your right breast started due to a lack of milk flow from the plugs.

Risks for a developing breast infection

Though finding the cause of the infection is less important than finding the right treatment, it may be helpful to know the risk factors of developing a breast infection:

Infrequent or incomplete milk removal
Your baby was recently ill with a staph infection
You have damage to your nipple skin or breast tissue
A topical bacterial infection improperly treated as thrush

If you've maintained regular, frequent, and complete milk expression, it's unlikely that the clumpy milk is due to anything else other than a bacterial infection.

Cause of clumpy breast milk

A coagulase positive staph strain like Staphylococcus aureus is the most common culprit.

Here's a video showing the tale-tell sign of a subclinical infection- milk that is chunky or turns gelatinous soon after expression. If you feel that you need to strain your milk, it's worth going in to get a culture and sensitivity test done.

Sometimes blood may also be present, which can be even more confusing to parents and providers alike. Even though this picture (left) looks a bit different than the other examples in this post (more like a blood clot than a lump of coagulated milk), this too is clumpy breast milk due to a subclinical staph infection. The appearance is due to blood in the milk, potentially from ruptured capalaries from expression or breast bleeding as a result of the infection .

Because some parents aren't aware that clumpy milk is a sign of a breast infection, subclinical mastitis may go untreated, resolving in due time. In other cases, subclinical mastitis develops into full-blown mastitis, which prompts parents to seek medical care. Rarely it just continues till weaning.

Breast milk fat plug vs. Clumpy breast milk

I've seen posts on the coveted fat plugs- where stored milk develops a fat cap and though not frozen, doesn't pour due to the amount of sticky fat "plugging" the top of the bottle.

If you're one to have experienced it already, you may now be curious about if the plugging phenomenon was due to a not so obvious case of mastitis.

You can rest assured that the odds are low that the plugging effect was due to anything other than a super thick lipid (fatty) layer in your breastmilk.

Generally speaking, clumpy milk due to mastitis will have one or two large masses but will not form a unified layer. Additionally, if left to sit, the lumpy milk may return to a liquid state, whereas the fat plug seen in expressed human milk tends to develop after a few hours left in the fridge.

Should I see my provider?

A culture done by your provider will give valuable information as to what bacteria is causing the infection, and the sensitivity & resistance test will show which antibiotic will be most effective. With that information, you then can choose which route of treatment you feel most comfortable with- treating it with prescription antibiotics or attempting a more natural/homeopathic route.

Can I feed my baby my milk?

Despite being super scary, there's little concern about feeding your baby your milk, whether expressed or directly from the breast. As you noticed, moving the fluid around or letting it set on your counter for a bit will liquefy the clump.