If you're in the DC area, the Federal Aetna open access HMO plan and the BCBS plan are pretty much the best, in my opinion. Neither one have deductibles; you just pay the copay and go about your day. My wife is pregnant now and we don't even have to pay the copay for the prenatal OB visits. Another member wrote about problems with Aetna, but we haven't had any problems with their federal plan. According to their brochure, you pay nothing for inpatient maternity services at the hospital- so you don't pay anything for the delivery and nursing care. No copays for prenatal care or the first postpartum care visit.
Kaiser is good, but I don't like that you have to use their facilities and doctors. Having to drive all the way to their facility for every single visit would be a complete pain and their plan doesn't offer anything that is better than the Aetna HMO plan or BCBS plan to make it worth that extra effort.