A cost-benefit analysis of prenatal detection of Down syndrome and neural tube defects in older mothers.

Infants of older mothers have an increased risk of Down syndrome. As public awareness of this disorder increases, so does the number of women requesting prenatal diagnosis for advanced maternal age. A cost-benefit analysis was done to determine the maternal age for which screening for Down syndrome is cost-beneficial. The analysis took into account the cases of neural tube defects which would be detected "incidentally" on amniocentesis, as all amniotic fluid samples have alpha fetoprotein levels measured. British Columbia (B.C.) provides a unique opportunity for such a study: single-year maternal age risk figures for Down syndrome based on virtually complete ascertainment are available; the Department of Medical Genetics Prenatal Diagnosis Clinic is the main referral centre for the province; B.C. has a universal medicare system which facilitates the calculation of medical costs and gives all women financially equal access to prenatal diagnosis. The study concludes that prenatal screening for Down syndrome is cost beneficial for women 34 years old or older at conception. A discount rate of 14% was chosen for this analysis and the effect of such a rate on the results is discussed.