['We evaluated whether the association of socioeconomic risk factors for trisomy 21 differed by type of maternal meiotic error.', 'We determined meiotic errors by DNA analysis for 150 trisomy 21 cases, and maternal lifetime exposures to low socioeconomic factors by questionnaire.', 'Mothers of meiosis II cases were significantly more likely to be exposed to four low socioeconomic factors than mothers of meiosis I cases (odds ratio = 9.50; 95% confidence interval = 1.8-49.8).'] Is maternal meiosis II nondisjunction in trisomy 21 associated with maternal low socioeconomic status?