Socioeconomic disparities in birth weight and body mass index during infancy through age 7 years: a study within the Danish National Birth Cohort

Abstract

BackgroundSocioeconomic inequalities in birth weight and in body mass index (BMI) later in childhood are in opposite directions, which raises questions about when during childhood the change in direction happens. We examined how maternal and paternal education and household income were associated with birthweight z-scores and with BMI z-scores at age 5 and 12 months and 7 years, and we examined the socioeconomic differences in the tracking of these z-scores across infancy and childhood.MethodsThe associations were studied in a cohort of children in the Danish National Birth Cohort, single born between 1997 and 2003, for whom information on body size from at least 1 of 4 time points (n=85 062) was recorded. We examined the associations using linear mixed-effects modelling.ResultsChildren from families with a low maternal and paternal educational level changed their body size z-scores upwards between birth and age 7 years. At age 5 and 12 months, there were no educational gradient. A low maternal educational level was associated with lower birth weight for gestational age z-scores at birth for boys (−0.199; 95% CI −0.230 to −0.169) and girls (−0.198; 95% CI −0.229 to −0.167) and higher BMI z-scores at age 7 for boys (0.198; 95% CI 0.154 to 0.242) and girls (0.218; 95% CI 0.173 to 0.264). There was not a similarly clear pattern in the tracking between different household income groups. However, a low household income level was associated with higher z-scores of both birth weight and BMI at age 7 years, but with a much weaker gradient at 5 and 12 months.ConclusionsThe educational gradient shifts from positive with birth weight, to none during infancy to inverse with BMI at age 7 years. In contrast, the income gradient was positive at birth and at 7 years and much weaker during infancy.

Parental Education and Genetics of BMI from Infancy to Old Age: A Pooled Analysis of 29 Twin Cohorts

“…Parental education is associated with BMI after early childhood, which parallels previous population based studies showing no association ( 29 ) or lower BMI ( 30 ) in the offspring of mothers with lower education before two years of age but a clear inverse correlation between the BMI of offspring and maternal education after four years of age. In early childhood, the lack of association between parental education and offspring BMI might be due to low birth weight associated with low parental education affecting BMI over the first years ( 29 ). Nevertheless, it may also reflect a change in the genetic architecture of BMI.…”

Relationship between socioeconomic status and weight gain during infancy: The BeeBOFT study

“…The associations between low maternal education level and more rapid infant weight gain in the first 6 months could largely be explained by shorter gestational age, and smaller weight for gestational age z-score. In line with previous studies, [ 36 – 39 ] our study found that infants with lower educated mothers had shorter gestational age, and had smaller weight for gestational age z -score. Weight gain during the first few months after birth is highly dependent on birth weight, since babies born with a smaller size tend to catch-up, while heavier babies tend to catch-down.…”

Complementary feeding practices and nutrient intakes of children aged 6–24 months from Bangladeshi background living in Tower Hamlets, East London: a feasibility study

“…On another note, several maternal parameters could be indirectly contributing to child overweight and obesity and risk of chronic disease. Firstly, pre-pregnancy maternal BMI could be contributing to the increased birthweights of infants, which may be persist into childhood and adulthood as overweight [69][70][71]. Moreover, there is an association between a Caesarean delivery and higher incidence of overweight and chronic disease for the children [72,73].…”