Int J Gynaecol Obstet. 2025 Nov 17. doi: 10.1002/ijgo.70671. Online ahead of print.
ABSTRACT
OBJECTIVE: Fetal size and gestational age are essential factors to consider when determining the timing of delivery between mothers and obstetricians in term pregnancies. Previous studies have shown that both fetal size and gestational age have associations with cognitive or academic outcomes. This study aimed to determine whether the association between gestational age (37-41 weeks) and child intelligence is moderated by fetal size in term-born children.
METHODS: Data were harmonized for four national cohorts in the USA, UK, Ireland, and Australia. Predictors included fetal size and gestational age. Fetal size was calculated using Fenton’s chart and grouped into three categories: Large for gestational age (LGA) (>90th percentile), appropriate for gestational age (AGA) (10th to 90th percentile), and small for gestational age (SGA) (<10th percentile). The outcome was intelligence quotient (IQ) scores at age 5 years. Linear models, contrast analyses, and point plots were employed.
RESULTS: In total, 30 035 term-born participants were included in the analysis. Overall, being born before 41 weeks and being born with SGA (but not LGA) were both negatively associated with IQ. No statistically significant interactions between fetal size category and gestational age at term were found. At each gestation from 37 to 41 weeks, being born SGA (but not LGA) was associated with lower IQ when compared to AGA. A small but clinically significant reduction in IQ (i.e., 0.23 IQ Z-score, equivalent to a 3.45 IQ difference) was found in SGA-born children who were born at 37 weeks compared to 41 weeks.
CONCLUSION: The association between gestation and child IQ at age 5 was not moderated by fetal size in term-born children. Regardless of gestational age at term, SGA (but not LGA) is consistently and unfavorably associated with poorer cognitive outcomes. The IQ at age 5 was only clinically meaningfully decreased in SGA children born at 37 weeks.
PMID:41243845 | DOI:10.1002/ijgo.70671
