Do adversities in the intrauterine and neonatal periods interfere with intelligence?

Investigate the effects of intrauterine growth restriction and socioeconomic status at birth on intellectual development.

Study conducted with 313 participants from a birth cohort from São Luís, in the state of Maranhão, assessed at birth and between 18 and 19 years of age. Variables at birth and early years of life (maternal age, maternal education, paternal education, occupation of the head of the household, family income, maternal gestational weight gain, intrauterine growth restriction, low birth weight, and breastfeeding duration), and education at 18 and 19 years were tested as determinants of intelligence quotient at 18 and 19 years using structural equation modeling.

Results: Intrauterine growth restriction did not have a total (p-value = 0.957), direct (p-value = 0.184), or indirect (p-value = 0.108) effect on the intelligence quotient at 18 and 19 years of age. Socioeconomic status at birth had a total positive effect of 0.406 standard deviations (p-value < 0.001) on its mean, corresponding to an increase of 4.54 points in the quotient for each increase in socioeconomic level at birth. This effect was not mediated by the other explanatory variables included in the model; however, a direct positive effect of 0.416 (p-value < 0.001) of socioeconomic status on education was identified, which showed a positive correlation (PC = 0.439; p-value < 0.001) with intelligence. Maternal age at birth also had a direct positive effect of 0.116 standard deviations (p-value = 0.042) on the mean intelligence quotient (QI) at 18 and 19 years, corresponding to an increase of 1.30 points for each 1-year increase in maternal age at birth.

Higher socioeconomic levels at birth directly affected the participant's intelligence and education positively, increasing the mean QI and education level at 18 and 19 years. A positive correlation was also identified between the two variables.