Signs of enhanced neuromotor maturation in children due to perinatal load with background levels of dioxins. Follow-up until age 2 years and 7 months.

We investigated psychomotor development (Bayley-test) and neuromotor functioning (Hempel-test) in a group of children with known perinatal load with background levels of dioxins. Bayley-test (n = 32) at 2 years, and additionally investigated growth, medical history, physical condition, TT4, TT4/TBG, TSH, AST and ALT at the age of 2.5 years did not reveal abnormalities, or differences between the high- and the low-exposure group. Although the Hempel-test was normal in all children (n = 31), we found in 22 out of 29 items less suboptimal scores in the high-exposure group; in five items this difference reached significance (p < 0.05). Total-score and subtotal-score (posture of legs and feet excluded) revealed lower "suboptimality-scores" with a wider range in the high-exposure group in comparison to the low-exposure group (total-score p = 0.008 mean 6.7 SD 3.6 and mean 9.3 SD 1.8 respectively and subtotal-score p = 0.06 mean 4.5 SD 2.9 and mean 6.1 SD 1.6 respectively (Mann-Whitney or Wilcoxon Two-Sample Test). Similar signs of enhanced maturation have been described in the tadpole due to low dosis of TCDD. Reflexes were higher (p = 0.02), with a wider range of findings in the high-exposure group. Our hypothesis is that these findings may be due to thyroxine agonistic action of dioxins, which is in accordance with the earlier described signs of relatively high thyroid function in the first 11 weeks of life in this high-exposure group.