BACKGROUND:

Research suggests that prenatal phthalate exposures affect child executive function and behavior.

OBJECTIVE:

We evaluated associations between phthalate metabolite concentrations in maternal prenatal urine and mental, motor, and behavioral development in children at 3 years of age.

METHODS:

Mono-n-butyl phthalate (MnBP), monobenzyl phthalate (MBzP), monoisobutyl phthalate (MiBP), and four di-2-ethylhexyl phthalate metabolites were measured in a spot urine sample collected from 319 women during the third trimester. When children were 3 years of age, the Mental Development Index (MDI) and Psychomotor Development Index (PDI) were measured using the Bayley Scales of Infant Development II, and behavior problems were assessed by maternal report on the Child Behavior Checklist.

RESULTS:

Child PDI scores decreased with increasing loge MnBP [estimated adjusted β-coefficient = -2.81; 95% confidence interval (CI): -4.63, -1.0] and loge MiBP (β = -2.28; 95% CI: -3.90, -0.67); odds of motor delay increased significantly [per loge MnBP: estimated adjusted odds ratio (OR) = 1.64; 95% CI: 1.10, 2.44; per loge MiBP: adjusted OR =1.82; 95% CI: 1.24, 2.66]. In girls, MDI scores decreased with increasing loge MnBP (β = -2.67; 95% CI: -4.70, -0.65); the child sex difference in odds of mental delay was significant (p = 0.037). The ORs for clinically withdrawn behavior were 2.23 (95% CI: 1.27, 3.92) and 1.57 (95% CI: 1.07, 2.31) per loge unit increase in MnBP and MBzP, respectively; for clinically internalizing behaviors, the OR was 1.43 (95% CI: 1.01, 1.90) per loge unit increase in MBzP. Significant child sex differences were seen in associations between MnBP and MBzP and behaviors in internalizing domains (p < 0.05).

CONCLUSION:

Certain prenatal phthalate exposures may decrease child mental and motor development and increase internalizing behaviors.