The objective of this study was to derive a customised birth weight standard curve in our institute and to compare the perinatal outcomes of small‐for‐gestational‐age (SGA) births classified by population‐based versus customised birth weight standards.

We surveyed 9052 normal singleton deliveries and generated customised standards by adjusting for maternal characteristics and neonatal gender. We compared adverse perinatal outcomes between SGA and non‐SGA births classified by both standards.

According to the population‐based standards, mothers of SGA infants were younger, thinner and shorter and had higher rates of nulliparity and female births. We adjusted for these maternal characteristics and neonatal gender in our customised standards. Multivariate analysis revealed that there were no differences in neonatal composite morbidity between the standards. However, infants classified as SGA by the customised standards showed a significantly higher rate of neonatal intensive care unit (NICU) admission than those classified by the population‐based standards.

Our study showed that customised SGA made no significant differences in neonatal composite morbidity, only a modest increase in NICU admission rate compared to population‐based standard. To clarify the association of adverse perinatal outcomes with customised SGA, larger studies are required.