Socioeconomic and seasonal variations in births. A replication.
D001741:Black or African American; D001723:Birth Rate; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008396:Maryland; D011247:Pregnancy; D012494:Sampling Studies; D012621:Seasons; D012923:Social Class; D012959:Socioeconomic Factors