Purpose: To examine the decision to undergo amniocentesis for trisomy 21, 47XXY, 45X, and unbalanced rearrangements routinely detected by prenatal karyotype.
Method: A decision-analytic model was designed for women deciding whether to undergo invasive prenatal diagnosis via amniocentesis. The model compared: (1) undergoing amniocentesis for detection of significant fetal chromosomal abnormalities with the concomitant risk of procedure related miscarriage to (2) forgoing amniocentesis and additional miscarriage risk and thus not discovering a potentially affected fetus. Baseline assumptions included a combined live-birth incidence of trisomy 21, 47XXY, 45X and unbalanced chromosomal rearrangements of 3.9/1000 and a 1/200 risk of a procedure related loss. Outcomes were assigned utilities and quality adjusted life years (QALYs) were calculated.
Result: In the baseline analysis, undergoing amniocentesis is the preferred option leading to an improvement of 0.023154 QALYs. Amniocentesis was superior to no amniocentesis in sensitivity analysis even when the risk of trisomy 21 was zero for women who would choose to terminate for 45, X or 47, XXY and remained true even for women who would choose not to terminate for other sex chromosomal rearrangements such as 47, XXX or 47, XYY.
Conclusion: The risks of amniocentesis have traditionally been compared to detection rates of Down syndrome, without considering other phenotypically significant chromosomal abnormalities routinely detected on prenatal karyotype. Women may consider this information in deciding whether or not to undergo invasive testing via amniocentesis and in the current model, it is associated with an increase preference for invasive prenatal diagnosis.
Candidate for the Lee B. Lusted Student Prize Competition