Genetic sonography: a cost-effective method for evaluating women 35 years and older who decline genetic amniocentesis

To determine whether offering genetic sonography to patients who decline invasive testing can increase the detection rate of trisomy 21 and is cost-effective.

The detection rate of trisomy 21, the number of pregnancy losses after amniocentesis, and the cost of detecting a single fetus with trisomy 21 were determined in women 35 years and older managed according to the following 3 policies: (1) universal amniocentesis, (2) genetic counseling for maternal age-associated risks for trisomy 21 followed by amniocentesis in patients who elected it, and (3) genetic counseling followed by genetic sonography in patients who originally declined genetic amniocentesis.

From a population of 40,143 women 35 years and older, the expected number of trisomy 21 fetuses was 349. After genetic counseling, 32% of patients declined invasive testing, resulting in detection of 70% of fetuses with trisomy 21. For universal amniocentesis, the cost to detect 1 fetus with trisomy 21 was $138,036. For the 32% who declined invasive testing after genetic counseling and underwent genetic sonography, the cost to detect a single fetus with trisomy 21 was a function of sensitivity and the screen-positive rate. For screen-positive rates between 5% and 25%, genetic sonography resulted in a cost savings between 14.3% and 18.8% when compared with universal invasive testing and resulted in a considerable increase in detection of fetuses with trisomy 21 (77% to 97%).

A policy of offering genetic sonography followed by amniocentesis to patients 35 years and older who originally decline invasive testing for the diagnosis of trisomy 21 is cost-effective and results in a higher overall detection rate for trisomy 21 without an increased risk of pregnancy loss.