I also highly recommend the OB & GYN Center in Frederick (97 Thomas Johnson Drive, www.obandgyncenter.com, I see you already have the phone number). I have gone to this practice for about eight years and have delivered three babies with them. I'm now 27 weeks pregnant with my fourth son, and I'm still just as pleased with the practice!
Right now, they have three doctors (one of them being female) and a female nurse practitioner. One of the things I like most about this practice is that it's smaller than most of the other practices in the area, so you receive more personalized attention (at least in my experience). You also know that one of three doctors will deliver your baby (they make sure you see each one at least once before delivery) as opposed to the possibility of not ever meeting the doctor who ends up delivering your baby in a larger practice.
I hope this information helps, and I wish you the best of luck with your pregnancy and finding the practice that best suits your needs.