This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous (Obs), Subject name: Gynaecology & Obstetrics
[{'content': "A multigravida at 35 weeks' gestation had the following finding on ultrasound. The following can be the causes except: \nSelect and explain. \nA. Diabetes, B. Posterior urethral valve, C. Rh alloimmunization, D. Anencephaly", 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B. Posterior urethral valvePolyhydramnios is diagnosed when the AFI >24cm or the single deepest pocket measures >8cm.Causes of polyhydramnios:a. MC cause of mild polyhydramnios = idiopathicb. Multifetal pregnancyc. Maternal diabetesd. Cleft lip/palate (GIT anomalies >NTD)e. Esophageal atresia/duodenal atresiaf. Anencephalyg. Chorangioma of placentah. Hydrops fetalis (Rh alloimmunization)i. TORCHj. Trisomyk. sacrococcygeal teratoma', 'role': 'assistant'}]