escaping backticks (`)

cross-posted on SO: http://stackoverflow.com/questions/29522699


A simple/naive m4 question, but I cannot find the correct answer.
I'd like to print a markdown header starting/ending a code section:

```
echo Hello
```

How do I create a GNU M4 macro containing the 3 backticks ? something like

define(`md_code',````')
md_code
echo Hello
md_code


Thank you,
P.