Results of routine first trimester screening tests and following invasive procedures during pregnancy

Objective: The purpose of this study is to show distribution of risk in pregnancies which underwent first trimester combined tests, and investigate general demographic and clinical characteristics of patients, underwent invasive diagnostic tests after screening tests. Methods: Combined test data of first trimester screening in 20082011 were evaluated retrospectively and cross-sectional. After the measurement of nuchal translucency (NT), double test was applied to complete combined test within the same day. Invasive diagnostic procedures were compared in terms of rate, indications, karyotype and postnatal outcomes. Results: A total of 1109 pregnant women were included. Their mean age was 31.07±3.73 years. Free-βhCG was 1.26±0.94 MoM and PAPPA was 1.16±0.65 MoM. Mean NT value was 1.60±0.67 mm. With threshold of 1/250, screening test was positive in 3.1% of the cases. Additional 22 cases due to first trimester screening and 19 cases due to second trimester screening had invasive procedures (6.4% in total). Invasive procedures revealed karyotype anomaly in 11.3%. Karyotype anomalies were more frequent in group (20%) with positive combined test compared to ones performed for other reasons like maternal anxiety. Conclusion: Although false positive rate is 3.1% in first trimester combined test, rate of total invasive procedures is more than double (6.4%). Number of invasive diagnostic procedures increased due to maternal anxiety of age and physicians evaluating only NT or double tests. With diagnostic procedures, chromosome anomalies reaches 11% and termination need reaches 10%. Invasive procedures performed due to anxiety of mother or physician revealed no chromosomal anomaly requiring termination.