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[Second trimester sonographic screening for Down's syndrome and other chromosomal abnormalities]
Violeta Dimitrova1, Todor Chernev, Valentina Mazneŭkova
1Hospital for Active Medical Treatment in Specialized Obstetrics and Gynaecology Maichin Dom, Department of Obstetrics and Gynaecology, Medical University, Sofia.
Akusherstvo I Ginekologiia
|November 21, 2002
Summary
Second trimester ultrasound effectively screens for chromosomal abnormalities, but has lower sensitivity for Down syndrome (DS) compared to serum screening. An abnormal sonogram can guide further prenatal testing decisions.
Area of Science:
- Prenatal Diagnostics
- Fetal Medicine
- Medical Imaging
Background:
- Second-trimester Down syndrome (DS) screening is crucial for prenatal diagnosis.
- Sonographic markers can aid in identifying fetuses with chromosomal abnormalities (ChrA).
- Comparison with serum screening provides context for ultrasound effectiveness.
Purpose of the Study:
- To evaluate the efficacy of second-trimester sonography for detecting DS and other ChrA.
- To compare sonographic screening performance with established serum screening methods.
- To analyze the predictive values of specific sonographic markers for fetal aneuploidies.
Main Methods:
- A detailed sonographic examination was performed on 1157 singleton pregnancies between 15-21 weeks gestation.
- The study included 18 fetuses with ChrA (13 DS, 5 other).
- Sonographic findings were analyzed for sensitivity, specificity, and predictive values, with data compared to prior serum screening studies.
Main Results:
- Ultrasound identified 77.8% of all fetuses with ChrA, with 100% detection for other aneuploidies but only 69.2% for DS.
- Increased nuchal fold thickness and echogenic bowel were highly sensitive markers for ChrA and DS.
- Individual markers like increased nuchal fold, echogenic bowel, and pyelectasis showed high positive predictive values for fetal DS, exceeding serum screening.
Conclusions:
- Expert second-trimester fetal sonography is a highly specific screening tool for ChrA.
- The sensitivity of sonography for DS is relatively low compared to other aneuploidies and serum screening.
- An abnormal sonogram may prompt invasive testing or refine DS risk assessment from serum screening.