Small for gestational age (SGA) is typically defined as birth weight < 10th percentile for age. Limited data are available regarding the growth of SGA preterm infants in relation to feeding type. We aimed to study SGA preterm infants fed fortified mother’s own milk (MOM) or preterm formula (PF) on growth patterns and catch-up growth at discharge and 2-year corrected age (CA). Our retrospective cohort study included data from medical records and follow-up questionnaires about SGA preterm infants born at < 37 weeks fed on MOM (n40) and PF (n40). Weight, length/height and head circumference (HC) were collected at birth, discharge and at 2-year CA, and Δ z-scores were calculated. The MOM group had significantly larger negative change in weight and length z-scores between birth and discharge, and smaller positive change in HC z-score (–0·47 (sd0·41)v.−0·25 (sd0·36),P= 0·01; −0·63 (sd0·75)v.−0·27 (sd0·75),P= 0·03; 0·13 (sd0·67)v. 0·41 (sd0·55),P= 0·04, respectively). Almost half of the MOM-fed infants experienced poor length growth by discharge compared with 22 % of PF-fed infants (P= 0·03). By 2-year CA, both groups had similar positive change in weight and HC z-scores, but MOM-fed infants had a slower increase in height z-score (0·64 (sd1·30)v. 1·33 (sd1·33),P= 0·02), and only 40 % had achieved catch-up height compared with 68 % of the PF group (P= 0·02). Our study indicates that fortified MOM-fed SGA preterm infants may need extra nutritional support in the first 2 years of life to achieve height growth potential.