Incidence of short stature at 3 years of age in late preterm infants: a population-based study

Objectives This study aimed to investigate the incidence of short stature at 3 years of age in a Japanese cohort of late preterm infants who were born at 34-36 weeks' gestational age (GA). We compared these late preterm infants with term infants (3741 weeks' GA), and evaluated the effect of birth weight on the incidence of short stature. Methods A longitudinal population-based study of 26 970 neonates who were born between 34 weeks' and 41 weeks' GA in 2006-2008 was conducted in Kobe, Japan. Of these neonates, 1414 were late preterm and 25 556 were term infants. The late preterm infants were then divided into three subgroups based on birth weight as determined by Japanese neonatal anthropometric charts for GA at birth: large-for-GA (n=140), appropriate-for-GA (AGA, n=1083), and small-for-GA (SGA, n=191). The incidence of short stature at 3 years of age was calculated in the late preterm group and compared with that in the term group, and between the AGA and SGA groups with late preterm birth. Results The incidence of short stature in the late preterm group was 2.9%, which was significantly higher than that in the term group (1.4%). Late preterm SGA infants developed short stature with a significantly higher (9.4%) incidence than that of late preterm AGA infants (2.1%). Conclusions The incidence of short stature in 3-year-old children who were late preterm infants has a 2-fold higher risk than that in term infants. The risk of developing short stature is increased 4.5-fold if they are SGA.