"Planned Parenthood health center can give you information about getting health insurance coverage and referrals for prenatal care."
......so can the yellow pages, the internet and the Health Dept.
They partner with other health care providers to fill in the gaps that that local clinic cannot provide. Mammograms, for instance, require trained and licensed staff as well as expensive radiographic equipment, so they "farm out" that diagnostic exam and help cover the cost of it for those w/o insurance.