ericamouse, I have just seen your post.
So, you need 26 weeks employment in total. Unfortunately, a career break is not counted as employment for MA purposes, but does count for your contracted OMP purposes.
To qualify for Maternity Allowance, you need to have 26 weeks (or part weeks) of work accrued.
So, what you could do, is try to negotiate returning to work early, and amass 22 weeks employment, as you have 26 weeks before your EDD. If you were able to do that, you would qualify, not forgetting that any annual leave you are due would count as employment also. So if you had 7 weeks due to you for the year, you could potentially only work for 15 weeks.
Normally, you could do 1 day per week, which would still qualify you. But you have to remember that this would reduce your OMP, which you don't want to do.
On that note, does your work have a policy regarding what counts as 'full pay' for your OMP? It has occurred to me that in the NHS, for example, the 'full pay' is taken as the average of your earnings for weeks 17-25 of pregnancy. If that was the case, your 'full pay' would be £0, so you would be paid in effect 26 weeks of £0. You need to find out if your company operates on 'full pay' meaning your normal salary, or full pay meaning your average pay over a standard time frame. This might affect your decision to return to work early.
Sorry to give you more to think about.