I bought a pair from Barneys (and had to return them because they were missing a giant crystal, great quality control, Barneys!) and they ran TTS for me. They are a bit narrow though so if you have wide feet you may not fit in them. The 38 was great lengthwise on me (I usually wear a US 8 in flats and US 7.5 in heels) so the 39 may be too long on you. I wish I could help you more but at least I can give you my experience with them so you can form your own opinions. Sometimes shoes just aren't made for our feet, you know?
Also, I didn't find them to be terribly comfortable or well-made... REALLY thin soles with no support and kind of flimsy. Not to mention, they were missing a crystal, so who knows how soon I would lose more if I wore them. JMO!