Problems in prenatal development
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Problems in Prenatal Development. Section 5-3. Types of Birth Defects. Some babies are born with serious problems that threaten their health or ability to live. These problems are called birth defects . Some birth defects are mild and can be corrected

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Problems in Prenatal Development

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Problems in prenatal development

Problems in Prenatal Development

Section 5-3


Types of birth defects

Types of Birth Defects

  • Some babies are born with serious problems that threaten their health or ability to live. These problems are called birth defects.

  • Some birth defects are mild and can be corrected

  • Other birth defects are severe and result in lifelong disabilities or even death

  • About 3 out of every 100 children born in the US have a birth defect


Types of birth defects1

Types of Birth Defects

  • Some birth defects affect the shape or size of the body

    • Example: misshapen foot or extra/missing finger

  • In some other birth defects, a part or system of the body does not function properly

    • Examples: blindness, deafness, mental retardation

  • Not all birth defects are apparent at birth – sometimes the abnormality does not cause problems until months or even years later


Causes of birth defects

Causes of Birth Defects

  • There are 4 main causes of birth defects:

    • Environmental factors

    • Hereditary factors

    • Errors in chromosomes

    • Combination of environmental and heredity factors

  • There are still about 60% of birth defects that scientists are not sure what they are caused by


Causes environmental

Causes – Environmental

  • Nutritional balance of mother’s diet

  • Any diseases or infections the mother has during pregnancy

  • Harmful substances – alcohol, tobacco, drugs

  • Other medicines that may help the mother but harm the baby

  • Exposure to outside hazards – like radiation


Causes hereditary

Causes - Hereditary

  • For each person, 5 or 6 recessive genes are imperfect

  • A single copy of these genes will have no effect on the development of that person – or the baby who inherits the gene

  • Sometimes, each parent passes on the same recessive defective gene – and sometimes the defective gene is dominant

  • In these cases, the baby may develop a birth defect


Causes errors in chromosomes

Causes – Errors in Chromosomes

  • Sometimes there may be too many or too few chromosomes in the baby’s cells – this may lead to a birth defect

  • This is not considered hereditary because the child does not inherit the condition from a parent

  • The most common birth defect of this type is Down syndrome


Causes errors in chromosomes1

Causes – Errors in Chromosomes

  • One child in every 800 births has Down syndrome

  • The risk increases if the mother is 35 or older

  • A child with Downs has an extra 21st chromosome

  • Because each chromosome carries hundreds of genes, the defect can interfere with development in many ways


Causes combination of environmental and hereditary

Causes – Combination of Environmental and Hereditary

  • Some birth defects result from heredity and environment working together


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