Intrauterine environment and cognitive development in young twins

Co-recovery of physical size and cognitive ability from infancy to adolescence: A twin study

This study tested phenotypic and biometric associations between physical and cognitive catch-up growth in a community sample of twins (n = 1285, 51.8% female, 89.3% White). Height and weight were measured at up to 17 time points between birth and 15 years, and cognitive ability was assessed at up to 16 time points between 3 months and 15 years. Weight and length at birth were positively associated with cognitive abilities in infancy and adolescence (r's = .16-.51). More rapid weight catch-up growth was associated with slower, steadier cognitive catch-up growth. Shared and nonshared environmental factors accounted for positive associations between physical size at birth and cognitive outcomes. Findings highlight the role of prenatal environmental experiences in physical and cognitive co-development.

Maternal depressive symptoms and children's cognitive development: Does early childcare and child's sex matter?

BACKGROUND

Maternal depressive symptoms (MDS) have been associated with poorer child cognitive development. Some studies have shown that childcare attendance moderates associations between MDS and child behavior problems, but we do not know if this is the case for children's cognitive development. Furthermore, few studies have evaluated whether associations between MDS and child cognitive development differ for boys and girls at school entry.

METHODS

This study used data from a population-based cohort study (n = 1364) comprising well-validated measures of children's cognitive development including academic readiness and language development in kindergarten and reading and mathematics achievement in first grade. Information on MDS was collected repeatedly from the child's age of 5 months to 5 years and on childcare from 5 months to 4.5 years. Moderation analyses were conducted to evaluate the differential associations of MDS with children's outcomes depending on the type of childcare attended and the child's sex.

RESULTS

Childcare type or child's sex did not moderate associations between MDS and children's cognitive outcomes except for MDS being associated with lower scores on reading achievement in first grade for girls with a very small effect size (sr2 = .003). Childcare attendance was associated with higher scores for children's cognitive development, however these associations disappeared after adjusting for covariates including child, mother and family characteristics. Regardless of MDS and childcare type, boys had, even after adjusting for covariates, lower scores on academic readiness (sr2 = .029) and higher scores on mathematics achievement (sr2 = .004).

CONCLUSIONS

Children's cognitive development at school entry was more strongly associated with maternal education, children's age in kindergarten and number of months of schooling in first grade than MDS. Contrary to associations between MDS and child behavior problems, childcare attendance did not moderate associations between MDS and children's cognitive development at school entry.

Placental mitochondrial DNA content is associated with childhood intelligence

BACKGROUND

Developmental processes in the placenta and the fetal brain are shaped by the similar biological signals. Evidence accumulates that adaptive responses of the placenta may influence central nervous system development. We hypothesize that placental mtDNA content at birth is associated with intelligence in childhood. In addition, we investigate if intra-pair differences in mtDNA content are associated with intra-pair differences in intelligence.

METHODS

Relative mtDNA content was measured using qPCR in placental tissue of 375 children of the East Flanders Prospective Twin Survey. Intelligence was assessed with the Wechsler Intelligence Scale for Children-Revised (WISC-R) between 8 and 15 years old. We accounted for sex, gestational age, birth weight, birth year, zygosity and chorionicity, cord insertion, age at measurement, indicators of socioeconomic status, smoking during pregnancy, and urban environment.

RESULTS

In multivariable adjusted mixed modelling analysis, each doubling in placental mtDNA content was associated with 2.0 points (95% CI 0.02 to 3.9; p = 0.05) higher total and 2.3 points (95% CI 0.2 to 4.3; p = 0.03) higher performance IQ in childhood. We observed no association between mtDNA content and verbal intelligence. Intra-pair differences in mtDNA content and IQ were significantly (p = 0.01) correlated in monozygotic-monochorionic twin pairs, showing that the twin with the highest mtDNA content was 1.9 times more likely (p = 0.05) to have the highest IQ. This was not observed in dichorionic twin pairs.

CONCLUSIONS

We provide the first evidence that placental mtDNA content is associated with childhood intelligence. This emphasizes the importance of placental mitochondrial function during in utero life on fetal brain development with long-lasting consequences.

The East Flanders Prospective Twin Survey (EFPTS): 55 Years Later

The East Flanders Prospective Twin Survey (EFPTS) is a registry of multiple births in the province of East Flanders, Belgium. Since its start in 1964, over 10,000 twin-pairs have been registered. EFPTS has several unique features: it is population-based and prospective, with the possibility of long-term follow-up; the twins (and higher order multiple births) are recruited at birth; basic perinatal data are recorded; chorion type and zygosity are established; since 1969, placental biopsies have been taken and frozen at -20°C for future research. Since its origin, the EFPTS has included placental data and allows differentiation of three subtypes of monozygotic twins based on the time of the initial zygotic division: the dichorionic-diamniotic pairs (early, with splitting before the fourth day after fertilization), the monochorionic-diamniotic pairs (intermediate, splitting between the fourth- and the seventh-day postfertilization) and the monochorionic-monoamniotic pairs (late, splitting after the eighth day postfertilization). Studies can be initiated taking into account primary biases, those originating 'in utero'. Such studies could throw new light on the consequences of early embryological events and the gene-environment interactions as far as periconceptional and intrauterine environment are concerned.