Problems in Prenatal Development

1. Problems in Prenatal Development Section 5-3

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. Causes – Combination of Environmental and Hereditary • Some birth defects result from heredity and environment working together