How to combat extreme postpartum hair loss? Injections into scalp? A cell +prp? Steroid scalp injections? Oral medication?

In my opinion,  a technique that gets your hair to cycle from telogen hair back to Growing anagen hairs will  shorten the duration of your hair loss. Some options include minoxidil, both oral or topical, PRP and low level laser. Should a hair loss expert determine that your postpartum hair loss is unmasking inherited hair loss, it should be treated.
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This is an important question. You might find the link helpful. Generally watchful waiting is most appropriate as these treatments have limited effectiveness and the hair will grow back.

Thank you for your question. The stress of pregnancy can cause synchronization of the hair cycle. This results in a greater shedding of follicles all at one time and will generally reverse itself over time. Two options you can consider for promoting hair growth are PRP (platelet rich plasma) and/or low level laser therapy. PRP can be combined with stem cells in the ALMI procedure in which a small amount of your fat is harvested into a syringe and then micronized. This results in a large number of regenerative cells that can be combined with PRP to stimulate your hair growth. Low level laser therapy is best done in the home to ensure higher compliance. I recommend the HairMax LaserBand which takes 3 to 5 minutes every other day. This will increase blood flow to the scalp, increase protein synthesis in the hair follicles and shift a larger proportion of the hair follicles into the growth phase. I hope this was helpful - Dr. Moore.

Most doctor will offer you all of the above, but your hair will return in a year or so after the pregnancy if you wait it out. Lasers will have no impact and if you do scalp injections of PRP, you won't know if you are normally recovering of the injections are benefiting you.  Steroid use is inappropriate