I dont know if it will be possible but perhaps you could speak to your local Health Authority about having flyers put into Bounty Packs that are given to New Mums in the Maternity Ward before they go home.
Another option is to contact the Company that goes round the wards taking the newborn pics and asking to partner them. I have recently had a wee boy and a company local to me done just that. The main company supplied the newborn pics but when i received them i also received details of the company where we have now booked with for a series of photo shoots similar to what you are offering. I did not respond to the flyer right away and the sent out a reminder about 6 weeks later.
I hope this helps. Good Luck.xx