How soon can a pelvic ultrasound detect a pregnancy when compared to a trans vaginal ultrasound?

Transvaginal U/S b/c of the nearness of the U/S probe to the uterus, provides a clearer more accurate picture and more detail is available, so 5 to 6 weeks after conception is about as soon as a reliable transvaginal U/S can provide information. Remember that variations in estimates of true gestational age can occur, as ovulation may be delayed in any given cycle.