My usual response goes something like this:

Use her name if she has given it, so

"Mary, I'm sure I do remember you, but I talk to so many mothers, that
names quite escape me, if you can briefly describe your situation when we
originally talked, I'm sure I can place you."  Frequently I DO remember
once she has done this, if not, I just fudge it a bit, and say "Oh yes,
and what is your current question?", as it probably dosen't matter
whether I remember or not.  Whether she was a client or a League call, I
tend to file my notes by date, so if I get the general time frame, then I
can find the right file folder.

When I was younger and better organized, I used to have a cross reference
card file.  I would file notes by date (in a file folder dated month &
year), then would make a card file also by date: noting Mom & Baby's
name, then would have an alphabetized card file of last names which would
have a brief note of the history, and dates.

I used to teach this method to all new Leaders I grew as well.  Along
with an upgrade version using silver & other colored paper clips that
alerted you if a call back was needed or if you needed to file this info
still.  About 10 years ago I was visiting one of these Leader's I 'grew',
and was watching her do her filing, I thought my what a nice system she's
using, and asked her about it.  She looked at me funny, answered my
question, and then said "But Kathe, you taught this to me!"  What can I
say, those pre-menopausal memory problems started a long, long time ago!

Kathe Catone, LLLL, IBCLC