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The cisterna magna in second-trimester fetuses with abnormal karyotypes
W J Watson1, V L Katz, N C Chescheir
1University of North Carolina, Chapel Hill.
Obstetrics and Gynecology
|May 1, 1992
Summary
Measuring the fetal cisterna magna during early pregnancy is not a reliable screening tool for detecting abnormal fetal karyotypes. This study found normal cisterna magna measurements in all fetuses with chromosomal abnormalities.
Area of Science:
- Prenatal Diagnosis
- Fetal Medicine
- Medical Imaging
Background:
- Fetal karyotyping is crucial for identifying chromosomal abnormalities.
- Sonographic markers are used to assess fetal risk for abnormal karyotypes.
- The cisterna magna is a posterior fossa structure that can be measured via ultrasound.
Purpose of the Study:
- To evaluate the utility of fetal cisterna magna measurement as a screening tool for abnormal fetal karyotypes.
- To determine if cisterna magna size correlates with fetal karyotype status between 14-21 weeks' gestation.
Main Methods:
- Sonographic measurement of the fetal cisterna magna was performed in 638 gravidas at 14-21 weeks' gestation.
- Participants were at increased risk for abnormal fetal karyotype.
- Measurements were compared between fetuses with normal and abnormal karyotypes confirmed by genetic amniocentesis.
Main Results:
- Fetal cisterna magna size significantly increased with gestational age in normal fetuses (P < .001).
- Twenty-eight fetuses had abnormal karyotypes (trisomy, translocation, sex chromosome abnormalities, triploidy).
- All fetuses with abnormal karyotypes exhibited normal cisterna magna measurements.
Conclusions:
- Fetal cisterna magna measurement between 14-21 weeks' gestation is not a useful screening test for abnormal fetal karyotype.
- This sonographic parameter does not effectively identify fetuses with chromosomal or structural abnormalities.