Objectives: To estimate changes in rates of prenatal testing for aneuploidy over a 5-year period in a large integrated health care system.
Methods: Data from the Kaiser Permanente Northern California cytogenetics laboratory and Regional Prenatal Screening Program were used to estimate rates of prenatal aneuploidy screening and diagnostic testing in females of all ages during 2006-2010. We estimated the number of chromosome abnormalities detected and the proportion of abnormal cytogenetic results. Dichotomous variables were compared using χ tests. Rates of use and aneuploidy detection rates were compared for trend using a linear repeated-measures model.
Results: Annual deliveries decreased during this period, from 36,276 to 34,314, whereas births to women aged 35 years or older increased from 21.8% to 22.7% (P=.004). The rate of aneuploidy screening decreased minimally from 76.1% to 75.4% (P=.04). Among women 35 years or older, the rate of screening increased from 53.1% in 2006 to 63.7% in 2010 (P<.001), whereas the percentage having diagnostic testing decreased from 40.9% to 26.8% (P<.001). Among women younger than 35 years old, the rate of screening decreased from 82.5% in 2006 to 78.9% in 2010 and the rate of diagnostic testing decreased from 4.1% to 2.8% (P<.001). Abnormal diagnostic test results increased from 5.9% to 8.2% (P<.001); the number of chromosome abnormalities identified overall was 7.2 per 1,000 births in 2006 and 6.7 per 1,000 births in 2010 (P=.43).
Conclusions: Offering comprehensive aneuploidy testing options to all pregnant women in an integrated health care system resulted in lower use and higher yield of diagnostic testing.
Level of evidence: II.