The relationship between gestational age, delivery, and fetal size, and neurodevelopment outcomes from infancy to...

The timing of delivery requires shared decision-making between pregnant women and obstetricians, balancing perinatal and long-term outcomes. Although prematurity and fetal growth restriction are recognized risk factors for adverse neurodevelopment, it remains unclear whether gestational age within the term period or fetal size at birth has the more enduring association with long-term neurodevelopment among term-born children.

To compare the persistence of associations of gestational age (37-41 weeks) and fetal size (defined as birth weight for gestational age) with early childhood neurodevelopment and adolescent academic performance.

Term-born children without congenital malformation from the Norwegian Mother, Father and Child Cohort Study (MoBa) were included in the study. Primary outcomes were parent-reported language and motor development at 6 months, 18 months, 3 years, and 5 years, and national test scores (Math, Reading, and English) at fifth grade (age 10-11 years), eighth grade (age 13-14 years), and ninth grade (age 14-15 years). Exposures were gestational age at term (37-41 weeks) and fetal size categories at birth: small-for-gestational-age (SGA, <10^th percentile), appropriate-for-gestational-age (AGA, 10-90^th percentile), large-for-gestational-age (LGA, >90^th percentile).

Among 92,551 term-born children, gestational age and fetal size showed distinct patterns of association with neurodevelopmental outcomes from infancy to adolescence. Earlier birth within the term range was associated with less favorable language and motor development in early childhood, but these associations diminished rapidly by 18 months and were minimal by age 5. In contrast, smaller fetal size (i.e., SGA) was associated with poorer academic performance that persisted throughout adolescence, including lower math scores at ages 10-11 years (β = -2.32, 95% CI: -3.15, -1.49), 13-14 years (β = -1.79, 95% CI: -2.52, -1.06), and 14-15 years (β = -1.85, 95% CI: -2.69, -1.02). The associations of gestational age and fetal size were statistically independent of each other.

Among term-born children, fetal size showed more enduring associations with long-term neurodevelopment than differences in gestational age within the term period. These findings suggest that gestational age and fetal size represent distinct, non-interchangeable sources of information when counseling families about long-term neurodevelopment after term births.