According to the Federal Communications Commission (FCC) a PSA is an announcement run by the media free of charge that promotes government or non-profit programs, activities or services, or other community-service announcements that are in the public interest, such as matters of health and safety. 

As a community service, broadcast stations will often run Public Service Announcements (PSAs) free of charge. Submit PSAs to any broadcast station that serves your targeted audience. Due to the controversial nature of abortion politicis, family-friendly stations may be most receptive to these ads.
 

Ask your station's ad department to send you information for programs that target 24-49 year-old women, or ask for other recommendations to reach health-oriented, family-oriented, conservative, or youth audiences. Most stations will recommend program, times and formats best suited to the audience you want to reach, e.g. talk shows, easy-listening music, contemporary rock, news, etc.

See more examples below and read Ads 101.