Increased milk output
While studies previously described improvements in milk output when double pumping, what remained unclear was the possible mechanism driving this increased volume. This potential mechanism has been elucidated in recent research (Prime et al. 2012). The study investigated mothers of term born infants, who participated in two pumping sessions, in a randomised order. On one day, the mothers double pumped for 15 minutes and on the other day, they single pumped sequentially for 15 minutes. The unique approach of this study was that a milk flow rate measurement device was used to measure milk ejection.
Dr Prime states: “Double pumping is not only faster, but it is more effective in removing milk. It stimulates an additional milk ejection. This results in 18 per cent more milk volume being pumped over a 15-minute pumping duration. Therefore more milk of higher fat content is removed, leading to better breast drainage and milk of a higher caloric value.”
Download the infographic here: "Optimising milk removal"
On the day the mothers double pumped:
- 18 per cent more milk volume was expressed on average
- A higher percentage of the available milk in the breasts was removed
- The pumped milk had a higher energy content
- An additional milk ejection occurred
- Double pumping (Sim) results in significantly more milk output at 2, 5, 10 and 15 minutes than sequential single pumping (Seq)
An additional milk ejection
The neuro-hormonal milk ejection reflex, with the key hormone oxytocin, is crucial for milk removal and maintenance of lactation. Milk is only available from the breast during milk ejections which are short, discrete increases in intra-ductal pressure, milk duct diameter and milk flow rate.
Milk ejections occur in both breasts at the same time, with the total number of milk ejections ranging from 2 - 14 between mothers (Prime et al. 2011a). This explains why milk removal varies between mothers; some mothers will remove milk quickly while others will need a little more time. While there is variation between mothers, for an individual mother the pattern of milk ejection is very consistent over the first year of lactation (Prime et al. 2011b).
When milk ejections were measured during double and single pumping, it became clear why double pumping yielded more milk volume and drained the breast better - an additional milk ejection occurred during double pumping.
Milk with a higher energy content
After double pumping for 15 minutes, the fat content of the total amount of pumped milk was 8.3 per cent, significantly higher than the 7.3 per cent measured during single pumping.
This is important for the following reasons:
- During breastfeeding/pumping, the fat content of the milk increases steadily. When milk has a higher fat content, it means that the breast has been drained better which is the case when double pumping.
- It is known that good breast drainage is very important for maintaining and increasing milk supply
- Milk with a higher fat content can be very important for babies that are not growing well.
Preterm babies’ small stomachs can only take very small volumes of milk, so it is essential to make sure that the milk is of high caloric value.
It is important to note that the overall results obtained during double pumping are not superior to what the infant is able to do during breastfeeding. The advantage of double pumping is that the results are closer to what the baby is able to do when feeding at the breast, and superior to what is obtained when sequentially single pumping.
Prime DK, Kent JC, Hepworth AR, Trengove NJ and Hartmann PE. Dynamics of milk removal during simultaneous breast expression in women. Breastfeeding Medicine 2011a; Vol 0(0); 1-6
Prime DK, Geddes DT, Hepworth AR, Trengove NJ and Hartmann PE. Comparison of the patterns of milk ejection during repeated breast expression sessions in women. Breastfeeding Medicine 2011b; Vol. 6(4): 183-190
Auerbach,K. Sequential and Simultaneous Breast Pumping: A Comparison. Int J Nurs Stud 27, 257-265 (1990)
Jones E, Dimmock PW and Spencer SA. A randomised controlled trial to compare methods of milk expression after preterm delivery. Arch Dis Child Fetal Neonatal Ed 2001; 85: F91-F95
Zinaman MJ, Hughes V, Queenan JT, Labbok MH and Albertson B. Acute prolactin and Oxytocin responses and milk yield to infant suckling and artificial methods of expression in lactating women. Pediatrics 1992; Vol. 89(3): 437-440
Hill PD, Aldag JC and Chatterton RT. The effect of sequential and simultaneous breast pumping on milk volume and prolactin levels: a pilot study. J Hum Lact 1996; 12(3): 193-199 g: a comparison. Int. J. Nurs Stud. 1990; Vol. 27(3): 257-265