Am enjoying the thoughts and discussion on this topic. If only we did
know how all these mechanisms worked.
I remember Kittie Franz talking about let downs years ago at a conference
somewhere in NY state. She asked how many felt MERs and how many
did not. Surprisingly there were a number of women who said that they
didn't think they had ever felt let down. Then she asked of those who felt
let
downs how many they felt during feedings. Most admitted that they were
aware of 5 to 10 let downs on each side.

Since then I have assured mothers that not everyone feels MERs but that
they could be having 5 to 10 on each side without them even knowing
about it.  Then I try to point out to the mother when they are occuring,
showing them the pause as the baby swallows. In my experience many
mothers are not feeling any MERs in the first three weeks and I think that
is common and probably normal. It seems to me that if the mother stops
worrying about let downs then things seem to go better. Of course we
are also keeping track of wet diapers and bms.
Out of interest I just checked the info on my last 20 first time  mothers.
I first saw them around day 5 or 6 and of these 20, 5 described MERs
as a tingling feeling  and 15 said they never felt let downs. I wonder
how typical that is ?  ( I see moms in their homes )
Ruth Bacon  IBCLC