M-L (M) fits hips 75-110cm
L-XL (L) fits hips 100-140cm
Unfortunately Partum Panties no longer stocks the S-M size
For C-Section Mamas, it is best to get a little bigger if you are between sizes so they are not too tight.
Although it is advisable to use something to monitor blood loss in the days immediately following birth, If you are after a more reusable option, check out Modibodi underwear. These comes in a range of sizes, styles and absorbencies. They have recently released a “MAXI” absorption which would be a good start for postpartum.