It's never too early to plan! I started planning mine about a year before I got pregnant!
Don't let worries about what 'might' happen stop you from making any plans, birth plans come in different parts and what might not apply in one section will in the next... for example, you plan a natural birth with baby going straight to the breast when born but you end up with a c-section. You can still have baby put straight on you and breast.
I spent a LONG time writing my birth plan and finally finished it last week.
It all depends on what you want, it's best to start with online birth plan templates and then build it up from there.
Just google a few and see which one's you like the most
