Speaking from personal experience here, not as someone who studies growth, I would say that I always knew when my son was having a growth spurt because he go from nursing every 1-2 hours to nursing almost continuously and fussing a lot at the breast, seeming to be frustrated that there wasn't enough milk to satisfy him at one sitting. The next day, or the second day, I would have *noticeably* more milk -- breasts fuller, firmer, heavier, spurting at let-down again when they hadn't for several weeks, return of the *tingling* feeling with let-down when I hadn't felt it for several weeks -- and he would go back to contentedly nursing once an hour or so, acting quite full and lethargic when he was done, and I could tell that my milk supply had clearly increased. Now, that doesn't mean that it permanently became higher -- over the next few days, as he nursed at his "old" rate, the symptoms of a larger supply would fade away again, until the next spurt. Following Michele Lampl's careful work on the non-linearity of early childhood growth (described earlier on Lactnet, babies don't grow slowly and steadily on a day-to-day basis, they stay the same, then "spurt" up very quickly -- when measured once a month, it looks slow and steady) -- I would say that children exhibit these days of trying to increase the milk supply either right before, during, or after (or maybe all three) a growth spurt as described by Michelle Lampl. I think the *only* way Dr. Hartmann would be able to detect this would be through careful day-to-day observations and measurements of a mother's breasts as she was experiencing this. I think it is such a transient thing -- usually only a day or two when baby is drastically increasing their nursing frequency, that it would be very difficult to detect clinically. IMHO, as always. Kathy Dettwyler