This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Genetics And Genetic Disorders, Subject name: Pediatrics
[{'content': "Antenatal diagnosis of all of these disorders is possible except: \nSelect and explain. \nA. Down's syndrome, B. Noonan's syndrome, C. Anencephaly, D. Severe combined immunodeficiency syndrome", 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. D. Severe combined immunodeficiency syndrome* There are various methods for antenatal detection of different congenital disorders. Antenatal ultrasound is one of them.* A first-trimester sonography can be used for confirming gestational age, singleton or multiple pregnancy and to measure nuchal thickness.* Second-trimester sonography detects fetal structural defects. Nuchal translucency is a powerful tool to detect aneuploidy such as Down's syndrome; it is also increased in patients with Noonan's syndrome, Stickler syndrome, and Miller-Dieker syndrome, among others.* Anencephaly is a NTD that can also be detected prenatally with sonography and maternal serum alpha-fetoprotein (MSAFP) screening test.* Prenatal genetic testing is not routinely done for severe combined immunodeficiency but is only available if a genetic cause has already been identified in the family.* If a genetic cause has been identified, DNA from the fetus can be removed and tested.", 'role': 'assistant'}]