Dear Sue,

Here is a citation regarding the difference between pumped and expressed
breastmilk.

Lang S,  Lawrence C, Orme R.  Sodium in hand and pump expressed human breast
milk.  Early human development 1994; 38:131-8.

For anyone who is interested, the abstract is as follows:

Sodium content was analysed in the expressed breast milk from 30 mothers.
Measurements were taken up to 24 days postpartum, during which time the
mothers expressed manually or by means of a pump.  Statistical analysis has
confirmed not only the known decline in sodium levels postpartum but has
also shown a significantly higher sodium content in manually expressed milk
compared to that from pump expressed milk.  This finding suggests that the
method of expression may alter the sodium concentration in human breast
milk, thus potentially reducing the amount of sodium supplementation
required by some preterm infants.


Shirley Gross M.D.,C.M., C.C.F.P.
Edmonton Breastfeeding Clinic