I think Mary's point is very well-taken re: research which suggests
limitations with test weighing.  However, I have had humbling experiences
which taught me the value of having a subjective way to measure my objective
observations of feedings.  I have two of the very nice Medela electronic
scales.  One I rent to provide for 24 hr test weights of infants I'm really
concerned about. ( It isn't out much as mostly I tell parents to rely on
diaper cts)  The other I keep in the office.  I almost never announce that
I'm going to do a test weight -- thereby avoiding performance anxiety, I
hope.  But I gen. do weigh babies at the beginning of a visit.  I sometimes
put them back on the scale after feeding just to get some sense of what
intake might have occurred.  Sometimes the info is quite useful.

For ex.  A woman came to see me with 5 wk old twins.  She said on the ph she
wanted  to learn better simultaneous positioning techniques.  When I saw the
twins I thought they looked very thin.  I asked to weigh them and both were
only 4-5 oz above birthweight, tho alert and well.  I asked her to show me
how she was feeding.  She got her twin pillow and showed me.  I altered a few
things.  We both noted swallowing -- or thought we did.  Babies fed for about
20 min. at which point she discontinued feed due to back strain.  Out of
curiosity I put them back on the scale.  I was stunned.  The little boy had
taken in .5 oz. and the little girl had taken in almost nothing.  I said wait
a minute here, no wonder they are so scrawny.  We put them back on, this time
one at a time, with real close attention to support of breast and deep latch.
 After 15 min in this well supported position, the girl took in 1.5 oz and
the boy 2 oz!  I told the mom that as much as I knew she didn't want to hear
this as it meant more time spent nursing, these kids couldn't yet be nursed
simultaneously.

She had resources, and opted to hire household help in the form of an au
pair, decided to give bottles occasionally, but fed infants one at a time
most of the day.  They began to thrive from then on, and ultimately got
strong enough to be fed simultaneously.

This was an instance in which a scale was quite useful to me.  I have more
than once been fooled by what looked like a good feed, but was not.

Barbara Wilson-Clay, BSE, IBCLC
priv. pract. Austin, Tx