I'm 9 months pregnant, and bought this to wear in the hospital rather than the itchy hospital gowns. It's pretty big on me, but the material is soft and cool (having a baby makes you soooo hot), which is exactly what I was looking for. For size reference, I am 5'3, 135 lbs pre-pregnancy and about 170 lbs now. I got the L/XL which again is pretty big, but I don't know if the S/M would have fit.