Before having my daughter I was in marketing and now I am a SAHM. So I can offer some advice. I have a chiropractor that I love and I am a walking advertisement for him and chiropractic care in general. So, first, understand a satisfied customer is a great advertisement. You need to buy ad space in local papers and give coupons like "Schedule a new patient evaluation and get your first adjustment free." Also, short basic facts/statistics about the benefits of chiropractic for pregnancy is helpful in an ad. Generally, you can create something simple with your logo. Paid advertising goes a long way, but it is a continual investment. You have to keep advertising to keep growing.
One idea that came to me is when I took the labor and delivery classes through the hospital before I had my baby, they had several people come in and talk about alternative medicines (aromatherapy, Reiki, massage therapy) for easing the pains of L&D. If I were you, I would call the hospital (maybe the education director) and ask if you could volunteer a small portion of time during each L&D class to educate pregnant women about the benefits of your services. Then you could pass out your business cards, and give them handouts and coupons to come into your office.
Also, look for opportunities to attend "health fairs," or baby products/services fairs. Sometimes they cost money to set up booths, but you can utilize your time to educate people.
In addition, I recommend attending church and participating in their activities and getting to know the congregation and letting them know you. Church is a great way to network and people often feel more comfortable coming to someone that believes like they do. Plus, people aren't afraid to recommend their friends to fellow church patrons. Plus, religious people have a reputation for producing babies. ;)
Just a couple ideas. I hope your business flourishes. We need more people doing what you are doing!!!