Objectives: To analyze trends in screening and invasive prenatal diagnosis over a 13-year period in relation to changes in the national prenatal screening policy.
Methods: Fetal karyotypes obtained following 11 045 prenatal invasive procedures between January 1999 and December 2011 were retrospectively reviewed. Referral indications were classified as medical and non-medical (anxiety). The number of tests per relevant chromosomal abnormalities (CA) detected in both groups adjusted for indication was calculated.
Results: A total of 414 CA were detected (3.8%), 355 of which were considered clinically significant. The percentage of invasive procedures has declined from 49% to 12%, although cases referred by anxiety have increased from 22% to 55%. A total of 3129 invasive procedures did not have any medical indication (28%) and 13 relevant CA (0.42%) were found in this group. In this low-risk series, the index "number of invasive testing needed to detect 1 relevant CA" adjusted for indication was 241.
Conclusions: Changes in our national prenatal policy through this 13-year period show an increasing efficiency of prenatal detection of CA. However, despite the intensifying screening policies, low-risk pregnant women show a growing demand for prenatal invasive testing and a baseline risk for cytogenetic abnormality of 1/241.
Keywords: Audit; Down syndrome; chromosome abnormalities; karyotyping; screening.