no-one has posted any scientific stuff yet so here you are:
information on breastfeeding and fertility from kellymom.com
Kellymom is my 'bible' where breastfeeding is concerned, and I like the fact that the authors back up their articles with the results of scientific research. I think the above page is pretty good and if you read some of the links at the bottom, covers the topic pretty comprehensively. It certainly helped me work out what's going on.
To add my story to the 'anecdotes', I'm still bf ds2, who is very nearly 2 years old, and this includes night feeds. He's fairly regularly away from me for up to 10 hours so I wouldn't say theh '4 hour' rule works with a child of his age (although he definitely makes up for it when he sees me!) I've only had two periods, one last January (so at around 18 months) and one last week. I don't know what brought on the first one - it was probably the 'menstruating without ovulation' mentioned in the article - but this time, it was definitely because we were apart for over 36 hours, and I only expressed twice in that time. Mind you, in between the two actual bleeding phases, I have felt I might be ovulating at times ('egg white' and other signs).
I can't remember when the periods came back with ds1, but then I fed him for far less time. Tbh, I agree with clairemagnolia that I was happy to avoid the monthly hassle for as long as possible, knowing they will come back at some point. (Funny, according to the Breakthrough Breast Cancer Generations questionnaire, I was defined as menopausal .) I'm a little annoyed with myself that I didn't express more when away from him two and a bit weeks ago. I would like a third lo but I'm in less hurry than dp appears to be .