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Pregnancy Timeline by SemestersDevelopmental TimelineFertilizationFirst TrimesterSecond TrimesterThird TrimesterFirst Thin Layer of Skin AppearsEnd of Embryonic PeriodEnd of Embryonic PeriodFemale Reproductive SystemBeginning Cerebral HemispheresA Four Chambered HeartFirst Detectable Brain WavesThe Appearance of SomitesBasic Brain Structure in PlaceHeartbeat can be detectedHeartbeat can be detectedFinger and toe prints appearFinger and toe prints appearFetal sexual organs visibleBrown fat surrounds lymphatic systemBone marrow starts making blood cellsBone marrow starts making blood cellsInner Ear Bones HardenSensory brain waves begin to activateSensory brain waves begin to activateFetal liver is producing blood cellsBrain convolutions beginBrain convolutions beginImmune system beginningWhite fat begins to be madeHead may position into pelvisWhite fat begins to be madePeriod of rapid brain growthFull TermHead may position into pelvisImmune system beginningLungs begin to produce surfactant
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Many common chemicals endanger brain development

Scientists, health practitioners and child advocates are calling attention to growing evidence that common and widely used chemicals endanger neurodevelopment in the fetus as well as in children of all ages.

Susan Schantz, professor of comparative biosciences at the University of Illinois, is one of dozens of signatories to a consensus statement on the negative affects of manmade chemicals within our environment. She and her colleagues study infants and their mothers to determine whether prenatal exposure to phthalates and other endocrine disruptors lead to changes in brain or behavior. This research, along with parallel studies in older children and animals, is a primary focus of the Children's Environmental Health Research Center at Illinois, which Schantz directs.

The report: "Project TENDR: Targeting Environmental NeuroDevelopment Risks," appears in Environmental Health Perspectives.

Chemicals causing the most concern include:

• lead and mercury
• organophosphate pesticides: agriculture and home gardens
• phthalates: pharmaceuticals, plastics, personal care products
• flame retardants known as polybrominated diphenyl ethers
• air pollutants from combustion of wood and fossil fuels
• polychorinated biphenyls (PCBs): electrical equipment

Although PCBs were banned in the U.S. in 1977, their use as coolants and lubricants in transformers and electrictronics persist for decades.

"These chemicals are pervasive, not only in air and water, but in everyday consumer products that we use on our bodies and in our homes. Reducing exposures to toxic chemicals can be done, and is urgently needed to protect today's and tomorrow's children.

"The human brain develops over a very long period of time, starting in gestation and continuing during childhood and even into early adulthood.

"But the biggest amount of growth occurs during prenatal development. The neurons are forming and migrating and maturing and differentiating. And if you disrupt this process, you're likely to have permanent effects."

Susan Schantz PhD, Professor, College of Veterinary Medicine, Beckman Institute for Advanced Science and Technology, University of Illinois.

Some of the chemicals of concern, such as phthalates and PBDEs, are known to interfere with normal hormone activity. For example, most pregnant women in the U.S. test positive for exposure to phthalates and PBDEs, both of which disrupt thyroid hormone function.

Schantz: "Thyroid hormone is involved in almost every aspect of brain development, from formation of the neurons to cell division, to the proper migration of cells and myelination of the axons after the cells are differentiated. It regulates many of the genes involved in nervous system development."

Phthalates also interfere with steroid hormone activity. Studies link exposure to particular phthalates with attention deficits, lower IQ and conduct disorders in children.

The report criticizes current regulatory lapses that allow chemicals to be introduced with little or no review of their effects on fetal and child health.

Schantz: "If it looks like a risk, we feel policymakers should make a decision that chemical could be a bad actor and we need to stop production or limit use. We shouldn't wait 10 or 15 years — allowing countless children to be exposed to it in the meantime — until we're positive."

Children in America today are at an unacceptably high risk of developing neurodevelopmental disorders that affect the brain and nervous system including autism, attention deficit hyperactivity disorder, intellectual disabilities, and other learning and behavioral disabilities. These are complex disorders with multiple causes—genetic, social, and environmental. The contribution of toxic chemicals to these disorders can be prevented. APPROACH: Leading scientific and medical experts, along with children’s health advocates, came together in 2015 under the auspices of Project TENDR: Targeting Environmental Neuro-Developmental Risks to issue a call to action to reduce widespread exposures to chemicals that interfere with fetal and children’s brain development. Based on the available scientific evidence, the TENDR authors have identified prime examples of toxic chemicals and pollutants that increase children’s risks for neurodevelopmental disorders. These include chemicals that are used extensively in consumer products and that have become widespread in the environment. Some are chemicals to which children and pregnant women are regularly exposed, and they are detected in the bodies of virtually all Americans in national surveys conducted by the U.S. Centers for Disease Control and Prevention. The vast majority of chemicals in industrial and consumer products undergo almost no testing for developmental neurotoxicity or other health effects. CONCLUSION: Based on these findings, we assert that the current system in the United States for evaluating scientific evidence and making health-based decisions about environmental chemicals is fundamentally broken. To help reduce the unacceptably high prevalence of neurodevelopmental disorders in our children, we must eliminate or significantly reduce exposures to chemicals that contribute to these conditions. We must adopt a new framework for assessing chemicals that have the potential to disrupt brain development and prevent the use of those that may pose a risk. This consensus statement lays the foundation for developing recommendations to monitor, assess, and reduce exposures to neurotoxic chemicals. These measures are urgently needed if we are to protect healthy brain development so that current and future generations can reach their fullest potential.

The National Institute of Environmental Health Sciences at the National Institutes of Health and the U.S. Environmental Protection Agency fund the Children's Environmental Health Research Center at the University of Illinois.
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Jul 8, 2016   Fetal Timeline   Maternal Timeline   News   News Archive   

"..the biggest amount of [brain]growth occurs during prenatal development." Susan Schantz PhD
Image Credit: Environmental Health Perspectives



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