Regarding the discussion of early onset of puberty:
I'm in nursing school now, hoping to finish up in May. This was a discussion last year in class, the idea of menstration occuring earlier and earlier in this country. My professor (some of her info in the past has been less than accurate about other topics such as breastfeeding and co-sleeping) said that the average age of first menstration for girls in the USA is now age 9. I didn't think that sounded right. In order for that to be true that would mean that half of the girls would be menstrating at ages 7, 8 and 9. And even though it's only anectodal evidence, I just know so few women whose daughters started menstrating anywhere near that early that I wanted to check it out for myself. 
So I did some research to see what I could find out. There is a government organization, I think it was NIH (National Institute of Health) in the US that does a health related survey, which I believe they said is done every year. In this survey they do ask about girl's onset of puberty and menstration. According to them they have not been able to verify that the age of first menses is occuring any sooner. This survey had listed the average age of first menstration, I can't remember how long at it was I think it was 40 years ago, as 12.8 years. And now it is 12.3 years. However, the researchers attributed this difference to the fact that on average Latino and African-American girls normally tend to get their first menstration at a slightly earlier age than Caucasian girls. And the percentage of Latino and African-American girls in the US population has increased significantly in the past 40 years. Also, I think that the fact that Latino girls get their menses earlier than Caucasian girls would also speak against the idea of breastfeeding correlating with a later onset of puberty and menses, because that is one population group that has a fairly high initiation rate and duration of breastfeeding.
So if anyone out there does know of a study that shows an earlier age of menstration I would love to see it, too. Because the breastfeeding advocate in me was very surprised to read that. I also have noticed that the formula-fed children that I know seemed to grow much larger and faster than my own children. It wouldn't have surprised me to find that they had their menses earlier. 
Also, I'm wondering being overweight might affect this too. I'm a LLL Leader I think I am beginning to notice a pattern regarding lacational amennorhea in the women attending meetings. Even among women who are nursing frequently, not supplementing and not having long separations from their infants, more often than not I am noticing it is the women who are overweight that are getting their periods back pretty quickly after the baby is born. And it usually seems to be the women who are thin or extremely thin that do not get their period back until their child weans, even up to 2 years or more. I wonder if it may be natures way of protecting women who are very thin and have very little fat stores from subsequent pregnancies. Long ago women were very thin when food was scarce. So maybe this is nature's way of protecting women from becoming pregnant again during times of starvation. So I wonder if weight might also be an issue with the onset of puberty and menses. Biologically her body knows that there are enough fat stores of maintain a pregnancy. Just a theory anyway. I hope this helps.
Sincerely,
 
Tricia Shamblin, LLL Leader, future R.N. (hopefully!)
Illinois, USA 

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