Does perinatal exposure to endocrine disruptors induce autism spectrum and attention deficit hyperactivity disorders? Review.

AIM: To provide an overview of studies on perinatal exposure in humans to endocrine disrupting chemicals (EDCs) in relation to autism spectrum (ASD) and attention deficit hyperactivity (ADHD) disorders. METHODS: A review of the literature (PubMed) was performed. Exposure-related keywords, including various chemicals, were matched with keywords describing outcome. Animal studies as well as publications not written in English were excluded. In total, 834 titles were retrieved. The final selection included 21 publications. RESULTS: Positive associations were found for ASD in relation to exposure to all chemicals investigated, which included hazardous air pollutants, pesticides and bisphenol A (BPA). Increased risks of ADHD or positive associations were found for exposure to polychlorinated biphenyls (PCBs), dialkyl phosphate (DAP) and chlorpyrifos. BPA, polybrominated diphenylethers (PBDEs) and low molecular weight (LMW) phthalates were positively associated with externalizing behaviour. Five of 17 studies did not find any association between exposure and ADHD. CONCLUSION: Perinatal exposure to EDCs appears to be associated with the occurrence of ASD as well as ADHD. Disruption of thyroid hormone function and gamma-aminobutyric acid (GABA)ergic mechanisms may offer an explanation for the observed relations; though, conclusive evidence in humans is limited.

Development of fetal and neonatal sleep and circadian rhythms.

The origin of sleep and circadian rhythms development is found during the fetal period. Both quiet (NREM) and active (REM) sleep are distinguishable during the last 10 weeks of gestation. Comparable to fetuses, low risk preterm infants recorded at 30-40 weeks postconceptional age, had a similar development of sleep i.e. an increase in quiet sleep and a decrease in indeterminate sleep. A further development in sleep organization characterized by increased slow wave and spindle activity during quiet sleep and coupling with circadian rhythm takes place during the first 6 months of life in both term and preterm infants.Circadian rhythm of fetal heart rate synchronized with maternal rest-activity, heart rate, cortisol, melatonin, and body temperature rhythms is present during the last 10 weeks of gestation. Although maternally influenced, circadian rhythm antenatally becomes ultradian at birth. Both preterm and term infants show a significant increase in circadian body temperature rhythm amplitude during the first 3 months of life.