...let me add that one can never assume anything when it comes to xenobiotics (any substance not part of a normal diet)...P-A-M is a pyrethrin-type insecticide, naturally-derived from chrysanthamum-type plants, and has a low order of toxicity in mammalian systems and apparently most reptiles as well...
...PRO-ZAP and other No-Pest-Strip (NPS) products contain dichlorvos, an organophosphate anticholinesterase insecticide, synthetically created, and these have a higher toxicity compared to pyrethrins...but also a potentially better insecticidal capacity...
...as in human medicine, use of any given drug/toxin (drug=toxin; dose-dependent)in/around
a pregnant animal has to be based on a risk/benefit analysis...in this case, if there is an existing mite infestation, it will ultimately lead to demise of the snakes, whereas proper use of the insecticides will not likely lead to toxic effects...therefore treat the snakes...
...Treatment: after discarding used substrate, replace with paper (I prefer unprinted newsprint as a standard substrate)...this will allow close inspection... holes in tubs should be taped over (frequently you'll find mites stuck to the tape as they attempt to exit the cage through the holes)...in a lidless rack system you can't really do anything about the space between the tub lip and "ceiling"...I prefer dichlorvos because it becomes vaporized, and can reach anyplace a mite can get, whereas P-A-M may not do that due to settling...assuming fresh NPS, depending on tub size, 1/2" x 1/2" up to 1" x 2" piece, placed in a 35mm film canister/Rx pill bottle with several 1/4" holes in it, placed in the cage for 12-18 hours every 10 days or so for 3 treatments...P-A-M will be useful for spraying the rack itself, area carpet or floor...
...to summarize, if you know your female(s) have mites, there is little option but to properly and effectively treat...
Scott J. Michaels DVM RPh
Serpent City