Girls, I need help?

Anonymous
My girlfriend says she has a thing implanted in her arm that girls use as birth control of some sort. I can feel it.
The other day she had her period..
I don't know what she called the thing otherwise I would search on Google..
So those of you who has that thing in your arm, do you still get your period? What does the implant do?
Does it prevent pregnancy?
Girls, I need help?
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