I have just been in hospital and cause of advice prior to going into labour- was well prepared.
I bought a pack of 5 low cut briefs from kmart for $7, then another pack of granny style the same. As I had an emergency caesar, I couldnt use the lowcut. But was able to use the big knickers and throw away each day. I was told to take 4 packets of pads to hospital, had one thick lot of pads that I wore with heavy loss initially then changed to the thin libra pads at home, my lochia comtinued for two weeks so used them till then. I was cutting them down in size by the end- but didnt want to waste them!
Hope this helps- be prepared for either a vag birth or a caesar!