Question:medium
Which of the following is the earliest to be diagnosed by ultrasonography (USG)?
Which of the following is the earliest to be diagnosed by ultrasonography (USG)?
Show Hint
The defect with the most obvious gross cranial abnormality is seen soonest.
Updated On: Jun 24, 2026
- Anencephaly
- Prosencephaly
- Meningocele
- Spina bifida
Show Solution
The Correct Option is A
Solution and Explanation
Rank these anomalies by how conspicuous they are to an early ultrasound probe. The defect that produces the most dramatic and easily seen abnormality of fetal anatomy will be the one picked up soonest.
Anencephaly wins on this basis. The fetal skull vault and the forebrain simply fail to form, so the normal rounded cranial outline is absent. This gross loss of the cranium gives an unmistakable appearance, and the failure of cranial ossification together with absent brain tissue can be appreciated from late in the first trimester into the early second trimester, which is sooner than the rest.
The competing options are harder and later calls. Holoprosencephaly needs evaluation of midline brain structures, while a meningocele and spina bifida require careful scanning of the spinal contour and posterior elements for more subtle bulges or splaying. Their diagnostic signs are generally confirmed later than the obvious cranial deficiency of anencephaly.
So the earliest diagnosis on USG belongs to anencephaly.
\[\boxed{\text{Anencephaly}}\]
Anencephaly wins on this basis. The fetal skull vault and the forebrain simply fail to form, so the normal rounded cranial outline is absent. This gross loss of the cranium gives an unmistakable appearance, and the failure of cranial ossification together with absent brain tissue can be appreciated from late in the first trimester into the early second trimester, which is sooner than the rest.
The competing options are harder and later calls. Holoprosencephaly needs evaluation of midline brain structures, while a meningocele and spina bifida require careful scanning of the spinal contour and posterior elements for more subtle bulges or splaying. Their diagnostic signs are generally confirmed later than the obvious cranial deficiency of anencephaly.
So the earliest diagnosis on USG belongs to anencephaly.
\[\boxed{\text{Anencephaly}}\]
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