Trends in the Prevalence of Down Syndrome (Trisomy 21) in Texas by Maternal Race/Ethnicity and Maternal Age Groups, 1999–2020

Down syndrome (DS) is a common chromosomal aneuploidy characterized by intellectual disability. Older maternal age is the strongest known risk factor for DS. The purpose of this study was to describe DS prevalence among major racial/ethnic groups stratified by maternal age, and to assess trends in prevalence over time in Texas. Cases with DS diagnoses delivered between 1999 and 2020 were identified from the Texas Birth Defects Registry (TBDR). Birth prevalence and crude prevalence ratios (PRs) by maternal race/ethnicity, maternal education, residence along the Texas-Mexico border, and Texas public health region (PHR) were calculated. Trends over time were assessed using Joinpoint. DS prevalence was significantly lower among mothers < 35 years compared to those 35+ years. Hispanic mothers, mothers with less than high school education, and mothers residing along the Texas-Mexico border had consistently higher PRs. Joinpoint analyses revealed significant increases in DS prevalence over time among non-Hispanic Black and Hispanic mothers. These findings identified significant increases in DS prevalence among non-Hispanic Black and Hispanic mothers compared to non-Hispanic White mothers, suggesting a potential widening of racial/ethnic differences in DS occurrence. Further research is needed to explore underlying drivers of these trends and to address differences in DS prevalence.