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11-13 week antenatal scan

Last revised by Dr Rohit Sharma on 17 Nov 2021

11-13 week antenatal (nuchal translucency) scan is considered a routine investigation advised for the fetal well-being as well as for early screening in pregnancy (see antenatal screening).

It includes multiple components and is highly dependent on the operator. Traditionally three factors are used to calculate the risk of trisomies:

Additional markers increase the detection rate and reduce false-positive rates:

Combining these factors with blood tests (i.e., dual marker) has been reported to achieve a nearly 95% detection rate for trisomies.

Apart from the screening protocol, early detection of major anomalies may be possible, and the checklist must include the following conditions:

See also

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Cases and figures

  • Case 1: Crown rump length (CRL)
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  • Case 2: Nuchal translucency
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  • Case 3: Fetal heart rate
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  • Case 4: Absent nasal bone
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  • Case 5: Ductus venosus flow (normal)
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  • Case 6
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