This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Diagnosis in Obstetrics, Subject name: Gynaecology & Obstetrics
[{'content': 'Best confirmation for pregnancy at six weeks? \nSelect and explain. \nA. USG for cardiac activity, B. Doppler, C. Estimation of serum beta-hCG in urine, D. Bimanual palpation', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. is a, i.e. USG for cardiac activityRef. Dutta Obs. 7/e, p 147With transvaginal scanning, cardiac activity is reliably seen in the uterus by 6 weeks, and by TAS cardiac activity by 7 weeks, cardiac activity confirms pregnancy.The level of hCG are not the best confirmatory test for pregnancy as hCG in plasma and urine are strikingly increased in women with hydatiform mole.Bimanual palpation can only detect uterine enlargement but the cause of uterine enlargement can only be detected by ultrasound.Confirmation of cardiac activity by Doppler can be done only at 10 weeks and not 6 weeks.', 'role': 'assistant'}]