Mary Ann Jones RN, BSN, IBCLC
Nancy E. Wight MD, IBCLC, FABM, FAAP

Many mothers of NICU infants are concerned about their milk volumes and wonder how much they should be making. NICU staff members may also wonder what a normal milk supply is and whether to expect any difference for mothers of premature infants. As human milk is the "gold standard" for human nutrition, we would all like to be able to support the mothers of fragile NICU patients in providing this valuable resource. The benefits of human milk for term infants are well recognized.¹ Current research suggests that human milk may especially benefit the preterm infant. ² Human milk provides nutrition, digestive enzymes, immunologic factors of many types, growth factors, hormones, and other bioactive factors, with new components discovered regularly. ³

The onset of lactogenesis II (when copious milk secretion begins) occurs on days 2-3 after delivery of the placenta. ⁴ Expected milk volumes for healthy post-partum mothers delivering at term are shown in Table 1 below.

Why would a mother need to produce so much milk, especially if she has a 500-1000 gram infant? Lactogenesis I (the hormonal preparation and growth of breast tissue) starts during pregnancy. ⁴ Some experts suggest that the mother of an extremely preterm infant may be at a disadvantage regarding milk production as she has not had the full time for breast growth and development. Also, Lactogenesis II may be delayed in mothers of very preterm infants. ⁵

Early, frequent, and effective breastfeeding or pumping appears to be the most important factor in establishing normal lactation. ^6-8 Prolactin bursts associated with the infant suckling or the mother breast pumping support the continued growth of secretory tissue in the maternal breast for several weeks or months after birth. ⁹ If the mother's body is not requested to make and maintain a certain amount of milk from the infant's birth, it will not be available when the infant is ready to consume a larger volume. That is why it is especially important for mothers of the tiniest infants to start pumping soon after delivery.

Research has shown the importance of establishing a full milk volume (> 750 mL/24 hrs) by day 10-14 postpartum in order to have sufficient breastmilk throughout hospitalization and for breastfeeding to continue after the infant is discharged. ^6,8 An easy way to simplify the goal amounts for mothers is to encourage them to:

• Pump 8 times in 24 hrs (to mimic the stimulation pattern of a term infant), and
• Make the goal of filling one volufeed (60 ml) per breast at each pumping session by the time the baby is 1-2 weeks old.