Trends in the use of second trimester maternal serum screening from 1991 to 2003

Purpose: To identify trends in the utilization of second trimester maternal serum screening, follow-up amniocenteses, and the detection of Down syndrome-affected pregnancies between 1991 and 2003. Methods: We reviewed all triple and quadruple maternal serum screening tests referred to the University of Connecticut screening laboratory from women with singleton pregnancies. For each calendar year, the total number of tests, proportion to women aged 35 or older, number of follow-up amniocenteses, and the number of prenatally and postnatally diagnosed Down syndrome cases were recorded. Results: A total of 109,469 women received screening. In 1991, the proportion of older women who received screening was 58% of that present in the Connecticut population but by 2003 this had increased to 83% (P < 0.001). In Down syndrome screen-positive pregnancies, there was no significant change in the rate of amniocentesis utilization (average 73%), but in false-positives, there was a decline from 70% in 1991 to 27% in 2003 (P < 0.001). Conclusion: Increased use of maternal serum screening by older women, use of second trimester ultrasound, and improvements in screening methodology have resulted in sharply reduced numbers of amniocenteses in unaffected pregnancies.