I'm a US trained labor and delivery nurse, but I lived in England for 6 years and my English mother-in-law was a midwife for 45 years. When I was going through nursing school, I had to do a paper on different reliefs of pain during labor and delivery. My mother-in-law very quickly informed me about Entanox. I did research on it, and although it is widely used in the UK, it is not used very often here...although, supposedly, more hospitals are integrating it into their systems. Our hospital does not use it. I always ask about it, because it's supposed to be a good relief of pain, it doesn't cross the placenta, and as soon as the woman stops inhaling it it's out of her system. I like the way it sounds!