Why does my hands-free wearable breast pump cup fog up, and can I prevent it?

Fogging occurs when warm breast milk and moist air contact the cooler cup surface, causing normal condensation.
To reduce it, start with a completely dry cup, let it warm inside your bra before pumping, and avoid very cool environments. While these steps may help, it may not be possible to prevent it completely. Fogging is harmless and expected with hands-free wearable pumps.