I am 5'2" and 105 lbs yet somewhat 'thicker' in the middle.  I ordered these in a Small, and the top especially was quite large for me.

Secondly, be aware this is a very THIN cotton.  Contrary to what many folks may believe, I actually find that HEAVIER cottons are more comfortable during the warmer months and help you to feel cooler..and to wick away any sweat.  Thin cottons such as that used for these PJs, I find they make me feel less comfortable...the thin cotton tending to STICK to me more.  Not only that, but thinner cottons look and feel more 'cheap'.

As such, I will be returning these....