Association between timing of diagnosis of trisomy 21, 18, and 13 and maternal socioeconomic status in Victoria, Australia: A population-based cohort study from 2015 to 2016.

Objectives: To explore the association between timing of diagnosis of common autosomal trisomies, maternal age and socioeconomic status (SES). Method(s): Retrospective study of all prenatal and postnatal cytogenetic diagnoses of trisomy 21 (T21), trisomy 18 (T18) and trisomy 13 (T13) in Victoria, Australia, in 2015-16, stratified by timing of diagnosis (prenatal <17 weeks gestation, prenatal > 17 weeks gestation, postnatal <12 months of age), maternal age and SES region (as assigned by postcode). Utilisation of prenatal testing following a liveborn T21 infant was ascertained via record linkage. Result(s): There were 160,230 total births and 817 diagnoses of T21 (n = 571), T18 (n = 139) and T13 (n = 107). The overall and livebirth prevalences of T21 were 3.56 and 0.47 per 1000 births, respectively. Compared with women from disadvantaged SES regions, women from advantaged SES regions were more likely to have a prenatal diagnosis of a trisomy before 17 weeks than after 17 weeks (p < 0.01) and less likely to have a liveborn T21 infant than a prenatal diagnosis (p < 0.01). There was a significant trend to higher livebirth rates of T21 with lower SES (p = 0.004). The majority (68.5%) of women who gave birth to a live infant with T21 did not utilise any prenatal screening or diagnostic testing. Conclusion(s): There is a significant relationship between lower SES, later prenatal diagnosis of trisomy, and higher livebirth rate of T21 in Victoria, Australia. The majority of livebirths with T21 were not preceded by any prenatal screening, suggesting significant disparities in utilization according to maternal SES.