Maternal age, parity, social class and sex ratio.
D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001722:Birth Order; D005260:Female; D006801:Humans; D008297:Male; D008423:Maternal Age; D010298:Parity; D012606:Scotland; D012744:Sex Ratio; D012923:Social Class