Children born full term with low birth weight have worse growth trajectories than those born preterm, according to study findings published in Clinical Endocrinology and Metabolism.

Infants born preterm or full term with low birth weight are at high risk of experiencing poor growth during childhood. However, the effect of low birth weight on growth trajectory remains unclear.  

To determine the effects of gestational age and birth weight on growth trajectories, South Korean researchers conducted a nationwide cohort study. Participants were children born preterm or full term with low birth weight who underwent 3 rounds of the National Health Screening Program for Infants and Children.

The researchers collected growth measurements (height, weight, and head circumference) from the program’s database and converted them into Z-scores. The study outcomes were growth data (short stature, underweight, microcephaly, and failure to thrive) at 2, 4, and 6 years of age.

The cohort included 1,150,508 children, of whom 41,454 were born preterm, 38,250 were born full term with low birth weight, and 318,816 were born full term with normal birth weight. The median birth weights of the preterm, full term and low birth weight, and control groups were 2.3 kg, 2.4 kg, and 3.2 kg, respectively.

At 2, 4, and 6 years of age, the incidence rates of short stature, underweight, microcephaly, and failure to thrive were highest among the full term and low birth weight group, followed by the preterm and control groups. Incidence rates of short stature and failure to thrive peaked at 4 years of age among the preterm and full term, low birth weight groups.

When the children were aged 4 years, the incidence rates for short stature were 5.2% for the preterm group; 6.0% for the full term, low birth weight group; and 1.9% for the full term group. The incidence rates for failure to thrive were 3.9% for the preterm group; 4.6% for the full term, low birth weight group; and 1.7% for the full term group.

The full term, low birth weight group vs preterm group had higher risks for short stature (adjusted hazard ratio [aHR], 3.15; 95% CI, 3.01-3.32) and failure to thrive (aHR, 2.58; 95% CI, 2.44-2.73) at 4 years of age.

Study limitations include missing data on mean parental height, the exclusion of biochemical data, and the exclusion of small for gestational age infants who were born preterm.

“In conclusion, our study demonstrated that infants born [preterm] and [full term, low birth weight] had a significantly higher risk for poor growth outcomes, a trend that persisted until preschool ages,” the researchers wrote. “In particular, the [full term, low birth weight] group had a worse growth trajectory than the [preterm] group. Most children achieve growth spurts by the age of 2 years; thus it is important to stratify high-risk populations requiring early intervention to help mitigate poor growth outcomes.”