COMBINED FIRST TRIMESTER SCREENING FOR FETAL DOWN SYNDROME AT THE SPLIT UNIVERSITY HOSPITAL CENTER: A SEVEN-YEAR EXPERIENCE.

The aim of this study was to present the results and to explore the success of combined screening at the Split University Hospital Center. A cross-sectional retrospective study was performed, including all pregnant women who underwent combined screening at the Split University Hospital Center from 2011 to 2017. Data were collected from the hospital archives. During the research period, a total of 6898 pregnant women underwent combined screening. With the high risk cut-off value set at 1:250, the sensitivity of combined screening was 81.0% and specificity 96.8% (AUC 0.929, 95% CI 0.859-1.000; p<0.001). The mean value of a priori risk of Down syndrome based on age was higher than the one calculated by combined screening (1:487.57 vs. 1:13216.9; p<0.001). The number of women who were a priori at a high risk of Down syndrome was significantly higher than the number of those at a high risk based on combined screening results (1457 vs. 239; p<0.001). With the increase in women's age, a statistically significant increase was detected in the mean value of a priori risk of Down syndrome, as well as in the risk based on combined screening results (p<0.001). Combined screening detected a high risk in 8.09% (118/1457) of pregnant women a priori at a high risk of Down syndrome, as well as in 2.22% (121/5441) of pregnant women a priori at a low risk of it. Thus, combined screening placed 121 pregnant women a priori at a low risk in the high-risk group. Down syndrome was subsequently confirmed in 17 (14.05%) women. Analysis of the combined screening results confirmed the validity of using the said fetal Down syndrome screening method in the study population of pregnant women.