Association between timing of diagnosis of trisomy 21, 18, and 13 and maternal socio-economic 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 socio-economic status (SES). Design: Retrospective study of cytogenetic diagnoses of trisomy 21 (T21), trisomy 18 (T18), and trisomy 13 (T13) in Victoria, Australia, in 2015 to 2016, stratified by timing (prenatal less than 17 weeks gestation, prenatal including or greater than or 17 weeks gestation, and postnatal before 12 months of age), maternal age, and SES region. Utilisation of prenatal testing following a live-born T21 infant was ascertained via record linkage. Results: Among 160 230 total births were 571 diagnoses of T21 and 246 of T18/T13. The overall and live birth prevalences of T21 were 3.56 and 0.47 per 1000 births, respectively. Compared with women from disadvantaged SES regions, women from high SES regions were more likely to have a prenatal diagnosis of a trisomy before 17 weeks than after (P <.01) and less likely to have a live-born T21 infant than a prenatal diagnosis (P <.01). There was a significant trend to higher live birth rates of T21 with lower SES (P =.004). The majority (68.5%) of women who gave birth to a live infant with T21 did not utilise prenatal testing. Conclusion: There is a significant relationship between lower SES, later prenatal diagnosis of trisomy, and higher live birth rate of T21 in Victoria.