I've heard about milk collectors and they sound super convenient. When should/shouldn't I use them?
Silicone milk collectors, also referred to as passive collectors (like a Haakaa), are super convenient, discreet and easy to use. However, they are intended to compliment breastfeeding. They do not replace baby nursing at the breast or a breast pump because they do not effectively drain the breast. Moms who need to pump to establish or maintain milk supply should not rely on silicone milk collectors.
How do they work?
Using a silicone milk collector prevents breast milk from being "lost" by soaking into clothing or breast pads. They suction to the breast and catch the "letdown". These are usually worn when baby is nursing on one side, to catch milk dripping from the other breast. Some moms wear them between feedings to catch those "letdowns" as well.
What should I do with the breast milk I collect?
Milk collected this way should not be the primary milk that is fed to baby. It may be mostly foremilk, which is thinner, more watery, and contains less fat and fewer calories. This milk is great for milk baths or can be combined with other pumped milk (of the same temperature) that was collected when the breasts were more thoroughly emptied.
A note of caution:
If a passive milk collector firmly suctions to your breast, and is used several times a day, it can increase how much milk your body makes. Moms who are dealing with oversupply issues should not suction collectors to their breasts.
Resource: