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.



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 clumps 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.