  The phase diagram of several itinerant ferromagnets reveals the common
feature. The phase transition temperature decreases with pressure increase and
reaches zero value at some critical pressure $P_c$ such that at low enough
temperatures one can expect critical behavior specific for quantum phase
transition. It is not the case, however. Being the second order at ambient
pressure the transition from paramagnetic to ferromagnetic state at high
pressures - low temperatures is transformed to the discontinuous jump. We
discuss the magneto-elastic mechanism of development of the first order type
instability at the phase transition to the ferromagnet state in strongly
anisotropic ferromagnet UGe2. Using the parameters characterizing the
properties of UGe$_2$ we argue the effectiveness of this mechanism transforming
the very weak first order type transition to the really observable one.
