Risks for Low Intellectual Performance Related to Being Born Small for Gestational Age Are Modified by Gestational Age

Abstract

OBJECTIVE. We sought to study whether the association between being born small for gestational age and risk for low intellectual performance was modified by gestational age.METHODS. A population-based cohort study was conducted of 352 125 boys who were born between 28 and 43 completed weeks of gestation from 1973 to 1981 in Sweden. Risk for low intellectual performance at military conscription, estimated as odds ratios with 95% confidence intervals was measured.RESULTS. Compared with men who were born preterm (28 -36 weeks) and had normal birth weight for gestational age, men who were born preterm and had a very low birth weight for gestational age were not at increased risk for low intellectual performance. In contrast, men who were born preterm with a very short birth length or a very small head circumference for gestational age faced a near doubled risk for low intellectual performance compared with their appropriate peers. Among men who were born at term (37-41 weeks), risk for low intellectual performance was increased among those with very or moderately small birth weight, birth length, or head circumference for gestational age.CONCLUSIONS. During early stages of gestation, growth in length and head circumference may be more important for intellectual development than weight increase. Future studies on size at birth and intellectual performance should consider also including anthropometric measurements other than birth weight. NTELLECTUAL PERFORMANCE, COGNITIVE function, and academic achievement are independently associated with both gestational age and measures of fetal growth. [1][2][3][4][5][6][7] We showed previously that risks for low intellectual performance related to short gestational age and indicators of reduced fetal growth (low birth weight, short birth length, and a small head circumference for gestational age) remain after controlling for socioeconomic and familial factors. 8 It has been hypothesized that the impact of fetal growth restriction on the child's long-term cognitive and motor development varies with gestational age at birth. 9,10 A number of studies reported increased risks for low intellectual performance and poor cognitive development among growth-restricted infants who were delivered at or near term. 6,11,12 Whether fetal growth restriction influences the long-term intellectual performance in preterm infants is still disputed. 13 In the present nationwide Swedish study, we investigated whether the associations between anthropometric measurements at birth and risks for low intellectual performance in early adulthood are modified by gestational age. METHODS Data SourcesThe methods of this nationwide Swedish cohort study are described in detail elsewhere. 8 Briefly, we included information from 4 population-based registries: the Swedish Medical Birth Register, the Swedish Conscript Register, the Multi-Generation Register, and the Population and Housing Census of 1990. Record linkage was possible using the unique National Registration Number that is assigned to each Swedish...

Associations of Birth Size, Gestational Age, and Adult Size with Intellectual Performance: Evidence From a Cohort of Norwegian Men

“…Consistent with a recent Swedish study (19), we observed an interaction between birth size and gestational age on intellectual performance (Fig. 1).…”

“…The study by Bergvall et al (19) seems to provide similar results, although they do not compare term and preterm births directly. It has been suggested that the importance of birth weight on neurodevelopmental outcome is lower than that of gestational age (19). The interpretation of our finding may be that compared with term births, birth size in preterm infants is less predictive of the intellectual potential.…”

“…However, despite loss to follow-up, we observed low scores for the lowest gestational age and birth size categories, as expected according to previous studies using somewhat different types of data and design (6 -11,13,19). Furthermore, our data compare with other Scandinavian studies using military draft data from practically the same time period and including males only (6,7,19). Still, the restriction to male participants may limit the external validity of our findings.…”

Carbohydrate and Energy Metabolism in the Brain of Rats With Thromboxane A2-Induced Fetal Growth Restriction

“…Surviving small-for-GA (SGA) infants have a higher incidence of neurological impairments including mental retardation and educational and/or behavioral problems (1)(2)(3). Several authors have reported that perinatal hypoxic ischemic brain damage may contribute to an increased prevalence of motor, cognitive, and affective disabilities in children born with FGR (4 -6).…”

28: First trimester alcohol exposure alters placental perfusion and fetal oxygen availability affecting fetal growth and development in a non-human primate model

“…Specifically, ethanol exposed fetuses showed significantly smaller fetal biparietal diameter and brain weight, consistent with prior MRI studies in murine 38 and rat 39-40 models demonstrating structural brain abnormalities resulting from first trimester ethanol exposure and microcephaly observed with fetal alcohol syndrome in human neonates 41 . Given that recent neuroimaging studies have revealed alterations in normal brain development in the setting of abnormal fetal growth [42][43][44][45] , it is possible that aberrant placental perfusion resulting in decreased oxygen availability contributed to the reduced fetal brain size. Interestingly, at G135, fetal and placental outcomes are less severe.…”