In very preterm infants, ex-utero growth retardation is associated with long-term growth failure and cognitive impairment. While human milk is the feed of choice, it may not meet the nutritional requirements of preterm infants. For this reason, human milk fortification is routinely practiced to ensure preterm infants have catch up growth. In this presentation, Simmer outlines the benefits, risks and limitations of human milk fortification. Evidence now clearly shows that accelerated postnatal growth, even in preterm infants, is associated with increased cardiometabolic risk later in life. Rapid catch up growth in the early years can have deleterious health consequences in adulthood. However, the optimal rate of catch up growth for preterm infants is yet to be determined. Even though human milk fortification is currently practiced, future research to ascertain the optimum growth trajectory for preterm infants is required.