<prompt> Best confirmation for pregnancy at six weeks:USG for cardiac activityDopplerestimation of serum beta-hCGBimanual palpation  <response>: In pregnant woman undergoing TVS Gestational sac :4 and half weeks yolk sac :5 weeks fetal node :5 and half weeks fetal hea :6weeks TEXTBOOK OF OBSTETRICS,SHEILA BALAKRISHNAN,Pg no:475,2nd edition 