Prenatal and childhood exposure to phthalates and motor skills at age 11 years

Abstract

Background: Previous reports suggest that prenatal phthalate exposure is associated with lower scores on measures of motor skills in infants and toddlers. Whether these associations persist into later childhood or preadolescence has not been studied.

Methods: In a follow up study of 209 inner-city mothers and their children the concentrations of mono-n-butyl phthalate (MnBP), monobenzyl phthalate (MBzP), monoisobutyl phthalate (MiBP), monomethyl phthalate (MEP), mono-carboxy-isooctyl phthalate (MCOP), and four di-2-ethylhexyl phthalate metabolites (ΣDEHP) were measured in spot urine sample collected from the women in late pregnancy and from their children at ages 3, 5, and 7 years. The Bruininks-Oseretsky Test of Motor Proficiency short form (BOT-2) was administered at child age 11 to assess gross and fine motor skills.

Results: The total number of children included in the study was 209. Of the 209 children, 116(55.5%) were girls and 93 were (45%) boys. Among girls, prenatal MnBP(b=-2.09; 95%CI: [-3.43, -0.75]), MBzP (b=-1.14; [95%CI: -2.13, -0.14]), and MiBP(b=-1.36; 95%CI: [-2.51, -0.21] and MEP(b=-1.23 [95%CI: -2.36, -0.11]) were associated with lower total BOT-2 composite score. MnBP (b= -1.43; 95% CI: [-2.44, -0.42]) was associated with lower fine motor scores and MiBP(b = -0.56; 95% CI: [-1.12, -0.01]) and MEP (b = -0.60; 95% CI: [-1.14, -0.06])was associated with lower gross motor scores. Among boys, prenatal MBzP (b = -0.79; 95% CI: [-1.40, -0.19]) was associated with lower fine motor composite score. The associations between MEP measured at age 3 and the BOT-2 gross motor, fine motor and total motor score differed by sex. In boys, there was an inverse association between ΣDEHP metabolites measured in childhood at ages 3 (b = -1.30; 95% CI: [-2.34, -0.26]) and 7 years (b = -0.96; 95% CI: [-1.79, -0.13]), and BOT-2 fine motor composite scores.

Conclusions: Higher prenatal exposure to specific phthalates was associated with lower motor function among 11- year old girls while higher postnatal exposure to ΣDEHP metabolites was associated with lower scores among boys. As lower scores on measures of motor development have been associated with more problems in cognitive, socioemotional functioning and behavior, the findings of this study have implications related to overall child development.

Keywords: Adolescence development; Motor development; Perinatal exposure; Phthalates.

Figure 1.. Adjusted estimated regression coefficients of prenatal phthalate metabolites and BOT-2 Total, Fine, and Gross motor composite score at age 11 in boys (squares) and girls (diamonds).

The x-axis represents the change in BOT-2 motor associated with a log_e unit increase in phthalate metabolite. Adjusted for prenatal specific gravity, maternal ethnicity, prenatal maternal demoralization, prenatal maternal alcohol consumption, quality of the home environment (HOME score), child BMI z-score at age 11, and child's age in months at BOT-2 administration. Bars represent 95% confidence intervals.

Figure 2.. Adjusted estimated regression coefficients of age 3 phthalate metabolites and BOT-2 Total, Fine, and Gross composite motor score at age 11 in boys (squares) and girls (diamonds).

The x-axis represents the change in BOT-2 motor score associated with a log_e unit increase in phthalate metabolite. Adjusted for age 3 specific gravity, maternal ethnicity, prenatal maternal demoralization, prenatal maternal alcohol consumption, quality of the home environment (HOME score), child BMI z-score at age 11, and child's age in months at BOT-2 administration. Bars represent 95% confidence intervals.

Figure 3.. Adjusted estimated regression coefficients of age 5 phthalate metabolites and BOT-2 Total, Fine, and Gross composite motor score at age 11 in boys (squares) and girls (diamonds).

The x-axis represents the change in BOT-2 motor score associated with a log_e unit increase in phthalate metabolite. Adjusted for age 5 specific gravity, maternal ethnicity, prenatal maternal demoralization, prenatal maternal alcohol consumption, quality of the home environment (HOME score), child BMI z-score at age 11, and child's age in months at BOT-2 administration. Bars represent 95% confidence intervals. *For MCOP metabolite at age 5, data were available for 116 women corresponding to 62 girls and 54 boys.

Figure 4.. Adjusted estimated regression coefficients of age 7 phthalate metabolites and BOT-2 Total, Fine, and Gross composite motor score at age 11 in boys (squares) and girls (diamonds).

The x-axis represents the change in BOT-2 motor score associated with a log_e unit increase in phthalate metabolite. Adjusted for age 7 specific gravity, maternal ethnicity, prenatal maternal demoralization, prenatal maternal alcohol consumption, quality of the home environment (HOME score), child BMI z-score at age 11, and child's age in months at BOT-2 administration. Bars represent 95% confidence intervals.