We study leptogenesis and baryon asymmetry generation in plasma of the early Universe before the electroweak phase transition (EWPT) accounting for chirality flip processes via inverse Higgs decays and sphaleron transitions which violate the left lepton number and wash out the baryon asymmetry of the Universe (BAU). The hypermagnetic helicity evolution proceeds in a self-consistent way with the lepton asymmetry growth. The hypermagnetic helicity plays a key role in lepto/baryogenesis in our scenario and the more hypermagnetic field is close to the maximum helical one the faster BAU grows up the observable value, Bobs ∼ 10−10.