From Memory Alpha...
The uniform was used primarily by background actors, though "Encounter at Farpoint" featured both Deanna Troi and Natasha Yar in skant-type uniforms, the latter only briefly. While Troi got a new look entirely for subsequent episodes (according to the Star Trek: The Next Generation Companion the uniform was referred to as the "Space Cheerleader" look), Yar remained in her jumpsuit uniform for the rest of her stay aboard the Enterprise, never donning the skant after the pilot episode. Male crewmembers wearing the skant were only seen in few episodes, "Encounter at Farpoint", "Haven", "Conspiracy", "Where No One Has Gone Before" and "11001001", though the footage seen in the last episode was re-used from "Where No One Has Gone Before". The skant was only seen in the first season and appeared four times in the second season, worn with black trousers underneath. After that it reappeared only once, in the flashbacks during "All Good Things...
Hope that clears it up for you. For the record I'm glad they got rid of it. The idea of a woman "working" in that uniform seemed unrealistic. The idea of a man
working in it was just outright silly.