J.S.
I'd ask if you googled, b/c that's how I found it. Anywho - here's the data
anyway:
0-6 months - 7% of BF moms have a period
6-12 = 37%
12-24 = 48%
over 24 = 8%
Here's another recent thread on the topic:
http://www.mamapedia.com/questions/2392679725085687809