Objective:

Prenatal screening tests have been developed to detect fetal aneuploidies. These tests and their combinations which are applied in first and second trimester and have different rates for detection of Down’s syndrome. The aim of this study was to compare the results of first and second trimester screening tests which were conducted independently in the same pregnancies.

Material and Methods:

The files of 1136 pregnant women having first and second screening tests independently were examined retrospectively. Patient’s ages, gestational weeks, first trimester CRL ve NT measurements were registered with their first and second trimester trisomy risk scores. Collected data were analysed with SPSS (Statistical Package for Social Sciences).

Results:

Mean age of the pregnant women were calculated as 26.6±5.8. %0.7 (n:8) of first trimester tests and %6.8 (77) of second trimester tests were reported as having high risk for trisomy 21. When the first and second trimester screening results in the same pregnancies were compared in terms of trisomy 21 risk scores; case numbers in terms of equal, decreased and increased risk were calculated as 55 (4.8%), 468 (41.2%) ve 613 (54.4%), respectively. While 11% (n:125) of those having decreased and increased risk were above 35 years old, this rate was just %0.1 (n:1) in those having no difference.

Conclusion:

In our study, 76 of 1128 patients detected as having low risk (<1\250) for trisomy 21 at the first trimester were encountered as having high risk (>1\250) at the second trimester test. Interpreting the tests independently will cause false positive results because of this we think that it is necessary to evaluate first and second trimester test results as entegrated.

Keywords: first trimester screening, prenatal screening, second trimester screening