1. Chapter 4.2: Problems in Prenatal Development

2. Losing a Baby Miscarriage Stillbirth
When the developing baby dies prior to the twentieth week of pregnancy
Stillbirth
When the baby dies after the twentieth week
About 15% of recognized pregnancies end in miscarriage
Medical professionals do not completely understand the causes
Stillbirth occurs in about 2% of pregnancies
Most common causes are problems in the placenta, abnormal chromosomes, poor growth, and infections

3. Birth Defects
A serious problem that threatens a baby’s health, and is present at birth
Hundreds of types of birth defects, each with its own set of symptoms
Approximately 120,000 babies are born each year in the U.S. with a birth defect

4. Types and Causes of Birth Defects
SOME BIRTH DEFECTS CAUSE AN ABNORMALITY IN THE STRUCTURE OF THE BODY
NOT ALL BIRTH DEFECTS ARE OBVIOUS AT BIRTH
SCIENTISTS DO NOT FULLY UNDERSTAND THE CAUSES OF MOST BIRTH DEFECTS
THEY HAVE DETERMINED THAT THERE ARE FOUR MAIN CAUSES FOR BIRTH DEFECTS:
Factors in the environment
Hereditary factors
Errors in chromosomes
A combination of environmental and hereditary

5. Environmental Causes
In the first few weeks after conception, a baby develops all the bodily systems needed for survival and a healthy, normal life
During this time the baby depends on the mother’s body for nourishment and oxygen
There may be environmental factors that the mother is unaware of that can affect the development of the baby
The nutritional balance of the mothers diet
Any diseases or infections the mother has during pregnancy
Harmful substances- Drugs and Alcohol
Some medicines
Air pollution
Exposure to X-Rays and certain chemicals

6. Hereditary Causes
Every person has approximately 20,000-25,000 genes that determine traits, such as eye color and height
Half from mother and half from father
Genes direct the growth and development of all body systems
Children usually get 5 or 6 imperfect recessive genes passed on to them
Sometimes both parents pass on the same faulty recessive gene
This causes the baby to have a birth defect
Recessive inheritance
Sometimes a child will inherit a defective gene that is dominant
If one parent passes on this gene it will cause the baby to have a birth defect
Dominant inheritance

7. Errors in Chromosomes
An error may occur when an egg or sperm cell is developing
This can cause a baby to have too many or too few chromosomes
The most common birth defect of this type is Down Syndrome
1 in 800 babies have this condition
Sometimes an error occurs causing an extra copy of chromosome 21
This can lead to increased risk of heart defects and leukemia

8. Interaction of Heredity and Environment
Some birth defects are caused by a combination of heredity and the environment
A child may inherit a tendency that may later lead to a heart defect
If a factor such as a drug or virus affects a baby during pregnancy, the baby will have a heart defect

9. Prevention and Diagnosis of Birth Defects
It can be challenging for a child born with a serious, birth defect to lead a normal, productive life
Family members are affected by the emotional and financial strain the defect causes
Couples who are planning to become parents should get a checkup to evaluate their overall health before trying to conceive
Because many women do not know they are pregnant in the early weeks, it is safer to quit smoking and drinking before there is a possibility of pregnancy
Once a woman is pregnant, she should visit her doctor for prenatal care

10. Genetic Counseling
Assess your risk of having a child with a birth defect that is caused by a defect in the genes
Family doctors can perform genetic counseling, but most patients are referred to a genetic counselor
Special lab tests may be performed
Blood and body tissue may be analyzed
Once testing is complete, counselors can tell a couple what their risks are for having a child with certain genetic birth defects

11. Prenatal Tests
More than 100 birth defects can now be detected before a baby is born
Alpha-fetoprotein (AFP)
Blood test performed on the expectant mother between weeks 15 and 20 of pregnancy
AFP is a protein produced in the liver of the fetus that is evident in the mother’s blood
Ultrasound
Test that uses sound waves to make a video image of the unborn baby
Monitors the development of the baby
Problems with the baby’s skeletal, circulatory, or nervous
system may be detected
3D ultrasounds that give a more detailed image

12. Prenatal Tests Amniocentesis Chorionic Villi Sampling
Withdrawing a sample of the amniotic fluid
The doctor uses the view from an ultrasound to guide a needle through the mother’s abdomen into the amniotic sac
Cells are taken to a lab and tested
Usually for women 35 or older
Involves some risk to the fetus and is performed only if there is a medical reason to do so
Done between 15th and 20th week of pregnancy
Chorionic Villi Sampling
Sample of the tissue from the membrane that encases the fetus
Tissue is cut or suctioned off and analyzed
10th and 12th week of pregnancy