The impact of first trimester screening and early fetal anomaly scan on invasive testing rates in women with advanced maternal age.

PURPOSE: To evaluate the acceptance of noninvasive screening for trisomy 13, 18, 21 and the impact on invasive testing rates in women at an age≥35 years.

MATERIALS AND METHODS: In a retrospective analysis from 2003-2006 including 13 268 women≥35 years old with singleton pregnancies and 3133 invasive procedures, we evaluated the prenatal detection rate of aneuploidies in two cohorts. Group 1: advanced maternal age as sole indication, group 2: additional abnormalities and/or suspicious maternal serum parameters. In an additional analysis from 1998-2006 including 31,076 patients≥35 years, we investigated the shift in time of sonography at 11+0-13+6, 14+0-17+6 and 18+0-22+6 gestational weeks (gw).

RESULTS: Among 13,268 women, 3133 invasive tests were performed with a significant decrease over time (-17%). 9% of women chose invasive testing after a normal ultrasound (group 1, n=1,267) and 14% in the case of additional markers (group 2, n=1,866). 102 cases of aneuploidy were disclosed. The proportion of detected aneuploidies was 0.86% in group 1 and 4.9% in group 2. No change in the overall detection rate (90-93%) was observed. The number of patients≥40 years increased significantly (+2.8%). There was an increase in examinations at 11+0-13+6 gw (+8%), a decrease at 14+0-17+6 gw (-10.3%) and no significant change at 18+0-22+6 gw over time.

CONCLUSION: Increasing numbers of women≥35 years of age rely on the individually adjusted risk figure to make a decision about invasive testing. The application of these selective procedures can reduce the rates of invasive testing with fewer losses of normal fetuses and led to an earlier diagnosis of aneuploidies.