Analysis of the distribution shift of detected aneuploidies by age independent first trimester screening.

ABSTRACT

INTRODUCTION: First trimester screening (FTS) became standard in non-invasive testing for chromosomal abnormalities in early pregnancy. The individual risk is calculated on the basis of a general background risk, which refers to the maternal age. A new method, Advanced Firsttrimester Screening (AFS) excludes the background risk in its algorithm. This study had the aim to analyze how the detection of aneuploidies is influenced by the in- or exclusion of the maternal age in the risk calculation. MATERIALS AND METHODS: The data of 15,228 first trimester screenings were recalculated with FTS and AFS. The study cohort was divided by age into nine groups and the numbers of detected cases were recorded according to the groups of age. RESULTS: Of 129 detected aneuploidies 90% got the same test results, disregarding whether risk assessment is performed including maternal age or not. FTS detected five aneuploidies at age 35 or older that were not recorded by AFS. AFS detected six aneuploidies that were not detected by FTS. Out of these, the oldest mother was 32 years old. DISCUSSION: When excluding the maternal age from risk calculation, the detection of aneuploidies showed a shift from older to younger women. Overall, the detection rate did not change significantly. However, the false positive rate was 25% lower with the exclusion of maternal age.