Supplementary Information (doc 36K)

Subjects and methods
A total of 241 mother-infant pairs (159 pairs in Thanh Khe and 82 pairs in Son Tra)
were enrolled at baseline. Follow-up examinations were conducted at 4 months, 1 year,
and 3 years after birth to assess development. Of the 241 pairs, 82.2% (122 in Thanh
Khe and 76 in Son Tra) participated in the 3-year follow-up assessment. A total of 43
pairs did not receive a follow up assessment, because they moved to other areas or were
absent on their test days. Moreover, 19 children refused to cooperate during the
neurodevelopmental testing, and the parents’ information was missing for 26 children.
Thus, the final sample for analysis included 153 mother-children pairs (98 and 55
children from Thanh Khe and Son Tra districts, respectively), representing 63.5% of the
original sample. No significant differences were found with regards to the
characteristics or breast milk dioxin levels between participants and non-participants, or
included and excluded participants. Infant body size parameters, including weight,
length, and head circumference, were measured at birth, 4 months, 1 year, and 3 years
of age.