Breastmilk does not lack any fats or nutrients for brain development like another poster stated! Thats totally false! Breastmilk contains super fats that are not found in any other substance on earth and cannot be repeated with formula. It also contains every single nutrient and vitamin a baby needs to grow and thrive. There is nothing lacking in it that requires synthetic vitamins unless mother has a bad diet. If mom is taking her prenatals, eating a fairly reasonable diet, and feeding baby on demand, there is not one good reason for synthetic vitamins for a breastfed baby, other than the reason I posted about below. And thats an easy fix, no expensive formula company supplied synthetic vitamins required.
Breastmilk only becomes deficient in vitamin D when the mother is deficient in vitamin D, so if you are still taking your prenatal vitamins, eating right and getting a few minutes of sunlight on your face or bare skin, your body will be producing enough vitamin D to pass through your breastmilk to your baby. Its true your breastmilk doesn't produce as much vitamin D as what is synthetically added to baby formula or with vitamins, but the GOOD news is, the vitamin D that IS in your milk is 100% absorbed by your baby, meaning all the Vit D you give him through your breastmilk is being absorbed. Whereas only about 20% of the Vitamin D in formula and a little more than that in the vitamins is absorbed by your babys body. So is really equals out, and the Vitamin D in your breastmilk is NATURAL and 100% absorbed by babies body and used easily, whereas the synthetic vitamins in formula or vitamin drops are just htat, synthetic and not easily absorbed, and very little of the actual vitamins are used by your childs body. and if you are taking your vitamins and eating right, and exposing yourself to a few minutes of natural light (and your baby too, just a few minutes of sunlight on his face is all it takes to produce enough vitamin D for his body... even once or twice a week.
So no, vitamins are not needed for breastfed babies as long as you are taking care of yourself and are mindful to let him have his face in the sun when its out for a few minutes. Thats really all it takes. Otherwise your breastmilk has all hte vitamins and minerals required for him. And its important to know that that Poly Vi Sol that doctors push on breastfed babies is made by the formula companies.... so in a roundabout way they are trying to gain teh business of breastfeeding mothers by saying bmilk isn't enough, take these expensive vitamins.
Its common for one side to produce a smaller amount than the other. Sometimes it seems like less when its really not, that breast just has more 'room' to store so it seems like less. Also what you pump is NOT an indicator of your supply, your baby can nurse out up to 4+oz more than any pump can. So if you are pumping 4oz from one side and only 2 from the other, it doesn't mean it produces 1/2 less, it just means that breast isn't responding ot the pump as easily. Very common. To up that side if you are concerned, only nurse on one breast per feeding. Don't switch hit. One breast for each nursing session, then use the other breast for hte next session. This not only allows your baby to get a full feed of foremilk and hindmilk (BOTH are necessary for growth and weight gain), but it tells your body exactly how much he is eating. Its a supply and demand. If you are switch hitting while nursing, switching from one breast to antoher after a set time, then your body thinks it only needs to make that amount. If you always start on one breast and finish on the ohter, the one you start with will produce less. So only one breast per feeding, don't switch. And if he seems satisfied with that breast that you think is producingl ess, then don't sweat it. He's an expert at knowing what his body does need.