I hate to say this, but the best way to do it is to prepare four tax returns. One set with him claiming her, one set with you claiming her, file with the set that works out best. If you both claim her, the IRS will apply tie-breaker rules, but it's legal for you to decide between you who's going to claim her.
What you're going to be balancing against is earned income credit vs. child tax credit vs. exemption (and possibly daycare). So if he's in a really high tax bracket he'll get more for the exemption. If one of you has a really low income, your child tax credit might be limited. EIC peaks at somewhere around 15k, so you can't just say if you make more or less, because it phases out on both sides. If you made 15k and he made 50k definitely, you claim her. If he made 15k and you made 4k, he should definitely claim her. But without knowing the numbers you'll have to go through the forms to figure it out.
It used to be you could split it but now only divorced or separated parents can split it. (ie if divorce paperwork says he claims kids every other year, but they live with mom, she gets EIC, he gets child tax credit and exemption).
Also, if you made less than the exemption ($3400) in your part-time work, he can claim you and the baby as dependents if you lived together all year long last year. And actually that would also prevent you from claiming the baby because you can't claim a dependent if you are or could be someone else's dependent.
Since you're a student you may want to also play with financial aid calculators or talk to someone at your school to see if it affects that, but that's out of my area of expertise. Other than I know you can find the calculators on www.collegeboard.com.
This is the first time in four years I haven't professionally prepared returns, so my knowledge is outdated by 1yr, but there aren't any huge shake ups that I've heard about.
Oh, and don't forget about child care expenses if you had any, it counts if you're using childcare to go to school too, not just work. And as a student, don't forget about your education credits!