[Maternal biochemical screening -- an approach for genetic prevention. part 1. first and second trimester screening]

The aim is to perform our eight-year experience on prenatal (matemal) screening for Down syndrome (DS).

Pregnant women underwent screening in second trimester (ST2) - 14(+4)-19(+3) gestational week using serum AFP and free beta-hCG biochemical markers. A more sensitive first trimester test has been implemented in 11(+0)-13(+6) gestational weeks since the end of 2009. This combined screening test (CST1) was based on US measurements of NT (nuchal translucency) and NB (nasal bones) supplemented by biochemical markers of serum free beta-hCG and PAPP-A. Uniform methodology, web-based software and system for laboratory quality control had been used. False positive ratios for DS were estimated at cut-offs 1/250 for Down syndrome and 1/100 for Edwards syndrome.

The test was performed on 17 468 pregnant women: 13 016 by biochemical screening 2 test (BHS2) and 4452 by first trimester test CST1. High risk for a chromosome disorder by BHS2 test was found in 1097 (8,4%) cases (5,96% < 35 years and 21,13% > 35 years). 7 fetuses were diagnosed with chromosome disease (5 fetuses with trisomy 21,1 - trisomy 18 and 1 - triploid); false positive were 1090 (8,4%). High risk for a chromosome disorder by CST1 test was found in 102 (2,3%) cases. 4 affected fetuses were diagnosed (3 with trisomy 21 and 1 with trisomy 13). Verified diagnosis for DS by first and second trimester tests were 43% (3 out of 7 cases) with 57% false negative results and 45,5% (6 out of 11 cases) with 54,5% false negative results respectively. Description of biochemical values/MoMs and US measurements are applied.

We comment on the importance of US measurements in CST1 test and correct analysis of biochemical and US markers in counseling of every individual patient, beyond final risk number.