How accurate is ultrasound done at 20 weeks for gender determination of fetus. is obstretics ultrasound with same accuracy. same question for 22 wks?

Mostly accurate: Ultrasounds at that point in your pregnancy is generally accurate. Remember, however, that the presence of a penis to diagnose a male is generally easier than the lack of one to diagnose a female. As one of my teachers once observed, "some boys are shy".

Depends.: My rule has always been: don't guess! if the fetus is in a poor position for viewing the genitals then no determination can be made. At 20 weeks, if the genital region is visible there is a very high level of accuracy for gender determination. It all depends on the skill of the person doing the scan.