This is one of those great examples of a really simple but effective study design. The researchers found 21 mothers who had given birth to 21 newborns (that’s one each, which makes it simple, because the issues might be different for women who have two or more babies to feed) and waited until 48-72 hours after they had given birth. Then, they asked them to express breastmilk. Half of the women did this manually first and then expressed with a pump, and the other half tried the different methods in reverse order. This was to remove the possibility of biased results based on whether the milk was collected from the first or second method used.
The contents of the milk samples were then analysed by machine and the results showed that, although there were no significant differences in the protein and carbohydrate content of the milk that was collected via the two different methods, the milk collected when the women hand expressed had a higher fat and energy content than the milk collected by pump. The researchers looked to see if the difference correlated with other factors, such as the mode of birth, maternal age or parity, but it did not.
The researchers have speculated that this difference may arise because the technique of hand expression is more likely to eject hindmilk (which contains more fat) than when women use a pump. It certainly raises some interesting questions about the value of touch and technology. I am aware, though, that there are lots of issues tied into this area, but Dr Jack Newman has already covered them on his website, so please check it out for more on expressing breast milk and to find out about some of the wider debates on expressing and pumping.