"Cold Calls" when applying for Accounting jobs...

One recommendation that I read for finding an Accounting job is to just send a cover letter and resume to some of the small to medium sized local firms. There are a few things that I would like some advise on.

Last May I graduated with my BA in Accounting from Michigan State, which is said to have one of the best Accounting programs in the nation. Due to getting pregnant for our 2nd child, I have just maintained a very part-time bookkeeping job instead of trying to get right into a full-time job. I have worked a temp assignment in this last month but it's still only on the lines of bookkeeping (and cleaning up their disaster Quickbooks file). I have done Accounting Assistant and Bookkeeping work since I was 19 back in 2005. So it's not like I have no experience, but I really want to take that next step (and have the ability to start paying on those outrageous student loans that I have accumulated).

So my main question I guess applies to more then just the "cold calls". Besides just general ideas for how to go about my cover letter, how do you suggest I go about addressing my delay in searching for a job? This baby is going to be born in September, and I was really hoping to really get into a job in December.

Applying for Accontant position