Perhaps you could ask about taking time out and coming back next academic year? If you could show them a clear plan for how you'd anticipate maintaining sufficient attendance, that might be a workable compromise?
It might also be worth looking at alternative schools/colleges? Sometimes the most "results-focused" ones aren't all that supportive of students with additional needs or other responsibilities (such as being a parent), and the intensive nature of those places can be difficult to cope with when you're also responsible for a small child and recovering from pregnancy and birth yourself! There are lots of very good colleges which are more flexible in their approaches, have on-site or local childcare services (or links with them), and which might be more supportive of your needs as a new parent and a student. Even if the school you're at has a good reputation on paper, if they're not supporting you then you might have a more rewarding time and have a better chance of fulfilling your potential at an establishment that's more committed to supporting you. Possibly something to consider?
It's also worth bearing in mind that, with a baby coming along, your life is going to change a lot and what you want to do in terms of time out from education and future career plans might well change too. Once your child is here, you might decide that you want to take longer to be at home with them, for example. And that's absolutely fine. These days, education is available at all ages, for everyone, and lots of people take time out for various reasons, or come back to education later in life. So, try not to worry too much about these school subjects at this college at this time. You have plenty of options - you can choose to take the options that are right for you and your baby, you don't have to follow one particular path here.
In terms of the school's reputation, the overwhelming majority of people honestly don't care which school you got your A-levels from in the long run. Good grades are good grades, and if you choose to go on to university, people are going to be more interested in your university studies and other experiences, rather than where you had your secondary school education.
I hope you've got good support around you. There are also some specialist initiatives which you can access through the NHS in various areas, which look to provide young mums with additional support. You might find it helpful to check what's available for your area?