As survival rates for preterm infants improve, attention is focused on improving the quality of survival through nutritional management. Necrotising enterocolitis (NEC) remains one of the most critical complications. Although no individual randomised controlled trial (RCT) has been sufficiently powered to examine the true effect of breast milk on the incidence of NEC in preterm babies,¹ a series of observational studies and a meta-analysis suggest a reduced incidence in those fed breast milk.^2–5 There is also evidence that human milk is better tolerated than formula, leading to a faster attainment of enteral feeding.⁶

Mothers of preterm infants experience physiological and emotional challenges, which may adversely affect breast feeding outcome following delivery. Therefore, it is not surprising that these mothers start and sustain breast feeding at lower rates than mothers of term babies.⁷ This is further compounded by the high levels of socioeconomic deprivation common in this population.⁸ Although there is a marked inverse relationship between gestational age and duration of breast feeding, it is not inevitable that lactation should fail, even in mothers of extremely low birthweight infants.⁹ This paper discusses the possible implications of a shortened pregnancy on mammary physiology and the lactating breast, and how to deal with any issues this might pose about the management of milk expression.

PHYSIOLOGY OF PRETERM LACTATION

Preterm delivery adversely affects initiation of lactation for the following reasons:

• mammary growth may be incomplete in a substantially shortened pregnancy, and poor placental function with low levels of placental lactogen may exacerbate this problem further¹⁰;

• the mammary epithelium may not be sufficiently prepared by the hormones of pregnancy to respond with efficient milk synthesis¹¹;

• lactation may be inhibited …