Task: Answer Verification
Input (English): Question: Is cephalic index a useful sonographic marker for trisomy 21 and trisomy 18?
Answer: In this retrospective study, CI was not found to be statistically different between the study and control groups. Although a trend towards significance was seen with T21, this difference is not clinically useful. There may be interethnic differences in the CI between fetuses. CI is not useful for aneuploidy screening by ultrasound.
Output (English): no