A dirty secret about pain relief in labour

We attended our second and final antenatal class, the one that's kind of scary, where we talked about pain relief and intervention. You know, the one that makes you kind of nervous and apprehensive and makes the voices in your head scream "you have to get a BABY out of you!!!"

Anyway, one thing did amuse me somewhat. I was curious to learn about pethidine, as it's one thing I don't know that much about. I learned that it's an opiate, and interestingly, that a lot of hospitals are now replacing it with its relative, diamorphine. Wait a minute. Isn't diamorphine the clinical name for heroin??? So, you spend your whole pregnancy avoiding alcohol and cigarettes and a heap of foods, and then in labour they shoot you up with heroin??? Come on guys, that's pretty funny!