Why might the result be weaker than usual?
This is the part that rarely gets said outright, and it genuinely affects your results.
The laser only removes hair effectively when it catches it in its growth phase (anagen) — that's when the hair is still connected to the follicle and conducts heat down to the growth point. Hormones largely control when a given hair enters its growth phase and when it enters its resting phase.
During breastfeeding, prolactin and estrogen levels differ from their pre-pregnancy state. That different hormonal rhythm translates into a different, less predictable hair-cycle rhythm — meaning the laser may not "catch" as many hairs in their growth phase as it would with stabilized hormones. The result can be weaker or uneven then, not because anything's wrong with the treatment, but because the hair isn't yet following its usual cycle.
