ABC figures for the six months from July to December 2007 are expected to show Bella's circulation to have dropped by around 30% from its 2006 ABC of 316,281 for the same period.
The January to June 2007 ABC figure was 247,390. Bauer would not comment on the matter when contacted by Media Week.
The fall comes despite Bauer's moves to reposition the title last March to younger readers with a revamp and a TV campaign.
One rival publisher said Bella's revamp was "too radical" since it tried to appeal to readers of Grazia or Look.
Earlier this month, publishing director Louise Newton left the title. Bauer would not comment on the reasons for her departure, but said that managing director David Goodchild is currently heading the magazine.
Bauer last week announced it had replaced Bella editor Jayne Marsden with Julia Davis, a former deputy editor of OK! magazine.
The mainstream women's weeklies sector has been facing tough competition from new launches in the real-life and celebrity sectors.
The next set of ABCs for the second half of 2007 are expected to reveal year-on-year circulation declines for NatMags' Best and IPC's Woman and Woman's Own.