Maternal age-specific rates of fetal chromosomal abnormalities at 16-20 weeks' gestation in Korean pregnant women ≥35 years of age

Objective: To provide estimates of maternal age-specific rates of fetal chromosomal abnormalities at 16-20 weeks' gestation for Korean women ≥35 years of age. Methods: Using the logistic regression method, we analyzed the amniocentesis data of 2,032 gravidas who had fetal karyotyping for the sole indication of advanced maternal age. Also, we compared the prevalence of trisomy 21 among countries using previously published datasets. Results: The incidence of aneuploidies increased exponentially with maternal age (p < 0.001). The expected rate of trisomy 21 was 3.7 per 1,000 gravidas at 35 years of age. Comparison with other countries showed that Japan has a significantly lower rate of trisomy 21 than North America (p = 0.041; 95% CI 0.522-0.986) and the UK (p = 0.011; 95% CI 0.474-0.909). Conclusion: These age-related risk figures are the first data for Korean women. Advanced maternal age was in this study ascertained to be a strong risk factor for chromosomal abnormalities; however, the age-specific risk can be influenced by racial factors.