title: Parental age, parity and sex ratio in births in England and Wales, 1968-77.
mesh_terms: D004739:England; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D008423:Maternal Age; D010298:Parity; D010331:Paternal Age; D012744:Sex Ratio; D014852:Wales