Concur with Mr. K. Unless the unit is uninhabitable (roach or bedbug infestation, no running water, no heat), they have no basis to legally walk away from the lease on a "worsening health" claim. Ask them to cite the law. (There isn't one.)
Please allow me to express my extreme annoyance with the claim that a high risk pregnancy = "worsening health". My second pregnancy was deemed high risk after an automobile accident induced pre-term labor. Nothing about that classification required moving out of my apartment - rather, it entailed bed rest, medications, and more frequent doctor visits.

