Association of perinatal factors and school performance in primary school Chilean children.

The associations between school performance and cognitive abilities with birth characteristics have mostly been studied without taking into consideration the effects of gestational age (GA). Our aim was to study the association between prenatal growth and cognitive function in term-born Chilean school children. A cohort of over 200,000 term-born fourth graders who took the regular national test for school performance was studied. Outcome parameters were language and mathematics test scores in relation to prenatal growth. A total of 256,040 subjects took the test and 220,940 were included in the final study sample. Prenatal growth was modestly, but significantly, associated with school performance. Adjusted ß coefficients for 1 cm increase in birth length were 1.28 and 0.77 for mathematics and language, respectively; the corresponding values for 100 g increase in birth weight were 0.59 and 0.34, respectively. Increased GA was associated with lower test scores. Adjusted ß coefficients for the birth measurements generally had a lower strength of association than those of socio-economic factors. However, the confounders most strongly associated with educational achievements were socio-economic factors, known to be associated with birth size. Lower socio-economic status is known to negatively influence both prenatal growth and cognitive function, supporting the overall importance of prenatal growth in relation to cognitive outcomes.

Prenatal growth and metabolic syndrome components among Chilean children.

The association of prenatal growth with metabolic syndrome (MS) components and insulin resistance (IR) in children has not been studied in Chile and most developing countries. Some associations found in developed countries are controversial. A retrospective cohort study was designed linking present information on MS components and IR in children with register-based information on birth weight (BW), birth length (BL) and gestational age (GA). Examinations included anthropometry and blood pressure (BP), as well as self-report of pubertal status. A fasting blood sample was taken to determine lipids, glucose, insulin and homeostasis model assessment (HOMA)-IR was calculated. The study cohort of 2152 children was on average 11.4 ± 1.0 years old. The prevalence of MS, IR and overweight were 7.6%, 24.5% and 34%, respectively. Elevated BP was negatively associated with dichotomized risk categories of the perinatal factors studied (BW, BL and GA). Contingency tables showed that high waist circumference (WC) and elevated BP had a U-shaped association with various categories of BW and BL, respectively. Stepwise linear regressions selected: (a) WC as inversely associated to GA and directly associated to BW, (b) BP as inversely associated to GA and (c) HOMA-IR as inversely associated to BL. Non-optimal prenatal growth seems to predispose to high WC, elevated BP and IR in school-age children, supporting the early life origin of several non-communicable diseases. Those associations were rather weak as estimated by the slopes of the regressions and probably reduced by their U-shaped nature; they would reasonably become stronger with a longer follow-up.