When do developmental delays present in preterm babies?

Late preterm infants-often overlooked in screening for developmental delays-experience more problems with reading and math in the preschool years than their peers who were born at either term or early term, according to a new study published in Pediatrics.

The researchers say their findings indicate that continued screening is important for late preterm infants, even if delays aren’t evident in early days.

“Despite similar development to full-term infants at 24 months, developmental differences in late preterm infants emerge by preschool,” says Prachi Shah, MD, associate professor of pediatrics in the Center for Human Growth and Development at the University of Michigan, Ann Arbor, and lead author of the study. “As such, keeping a close eye on the development of late preterm infants is warranted into preschool and kindergarten.”

More: Improve your practice with behavior evaluation and management portals

The goal of the research was to compare developmental outcomes in preschool and kindergarten children based on their gestational age at birth. Researchers focused on comparing the outcomes of late preterm, early-term, and term children.

The study included 1000 late-term, 1800 early-term, and 3200 term infants. The children were evaluated by direct assessment at 9 and 24 months of age using the Bayley Short Form Research Edition Mental T-scores, and at the preschool and kindergarten levels using the Early Childhood Longitudinal Study.

The research team found that both term and early-term infants had better outcomes than late preterm infants overall, and that the developmental delays in the late preterm group did not emerge until the preschool or kindergarten years.

There are more than 400,000 late preterm infants-between 34 to 37 weeks’ gestation-born each year, representing 75% of all preterm births. Although it has been thought that late preterm infants suffer from fewer long-term effects than preterm infants born earlier, the research teams say there is now increasing evidence that late preterm infants have higher rates of learning disabilities than children who were born at 37 weeks’ gestation or later.

Children born in the later preterm period have been shown to exhibit lower school readiness, spatial abilities, verbal reasoning, educational achievement, and poorer school performance in the early school years than their peers born after 37 weeks, according to the report.

Researchers say late preterm infants demonstrated lower cognitive skills at 9 months of age than other gestational age groups, but any impairments found with the 9-month assessment seem to have disappeared by the 24-month follow-up.

NEXT: What happens when they reach preschool age?

By the preschool years, however, the delays were once again observed. Children born at late preterm had lower reading and math scores than children born at full-term, but their scores were better than children born at early term, the researchers found.

At the kindergarten level, children who were late preterm infants fared worse in some areas, but not others, demonstrating lower reading skills than children born both at term and at early term. Math skills, on the other hand, were equal among all the gestational age groups by kindergarten.

The study reveals a few possible explanations for the delays, specifically the neurodevelopmental immaturity-lower brain volume and less neural connectivity-in the brains of late preterm infants.

“These structural differences in the brains of children born late preterm, including lower gray matter volume present in infancy and school age, may be associated with the suboptimal development in early reading and math skills we identified, similar to that which has been observed in children born full term,” the researchers say. They note that the absence of delays at the 24-month assessment could be from limitations of the testing tools or delays that are too subtle to become obvious until a more advanced age.

Next: Do early motor milestones predict later cognitive skills?

Late preterm infants born just slightly preterm are typically not followed in neonatal follow-up clinics, Shah says, making close monitoring before entering school that much more important.

“For the child born late preterm, the preschool and kindergarten health supervision visits are an important opportunity to inquire about skills in early reading and math including letter and word recognition, letter sounds, number recognition, counting, and recognition of colors and shapes, which are some foundational skills for school readiness,” Shah says. “Promoting early literacy and numeracy in the heath supervision visit is indicated for all children, but may be especially helpful for children born late preterm. Parents should be encouraged to provide opportunities to foster skills in early reading and math, including reading to children, encouraging conversation around book sharing, and practicing counting and pattern recognition.”

Early intervention is key in instances where delays are found, Shah adds, suggesting that late preterm children with suboptimal early reading and math skills in the preschool and kindergarten years be referred for psychoeducational testing and possibly more in-depth developmental testing.