A mother is depleted of iodine, magnesium and especially vitamin D3 during breast feeding. I prefer to just supplements these with kelp, magnesium chloride (or magnesium citrate) and 10,000 i.u. of vitamin D3 to raise the immune system. Sometimes a mother is low on cobalt and molybdenum, where cobalt comes from vitamin B12 injections or sublingually. Molybdenum is obtained from a chemical supplier in form of sodium molybdate, and it also helps greatly night blindness, a condition I sometimes have myself. If a small budget is available by you, it helps to get some hair mineral analysis to see what you are deficient in. Lead and mercury is relatively high in United States, as manufacturing standards try to produce any foods below 10 ppm, while safe levels is deemed to be below 2 ppm. So there is an 8 ppm dangers here that the mainstream authorities is overlooking. Further food processing with added heavy metals doesn't count, so it may well be over 10 ppm of lead and perhaps much higher mercury then they actually anticipated. What is most interesting is common metal toxicity at least from my water faucet is that most faucet systems are brass, (especially the inside) which is bad news while the exterior of the faucet is a nice chrome look. It's bad news because they are the major source of copper and zinc, which causes alzheimer and not just the aluminum.
One other thing that mother might be more deficient in is colostrum and taurine. Colostrum increase the mother's immunity and is transferred to the child. Taurine is essential in baby's nutrition and I believe mother should be given some taurine supplement as a result, such as 500 mg x 3 of taurine a day, at the very least.