Birth Defects

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Birth Defects
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What is a birth defect?

• Babies that survive pregnancy but are born with
  serious problems that threaten their health or
  even their lives.
• There are hundreds of types of birth defects,
  each with its own set of symptoms.
• Approximately 150,000 babies around the world are
  born each year with a birth defect.
• Not all birth defects are apparent at birth.

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Four Major Causes of Birth Defects

• Environmental
• Hereditary
• Chromosomal (Errors in Chromosomes)
• Multifactorial (Interaction of Heredity
  Environment)

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Environmental Causes

• There are several environmental (external)
  factors that can affect the development of the
  baby. Such as
• Nutritional diet of the mother
• Diseases or infections
• Harmful substances the mother consumes
  (prescription drugs, alcohol, illegal drugs)
• Exposure to hazards such as X rays

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Hereditary Causes

• Genetics can affect the development of the baby
• Every person has approx. 20,000 25,000 genes
  that determine everything from eye color to
  directing the growth and development of every
  system in the body.
• Children typically get 5-6 imperfect recessive
  genes passed on to them.
• Where parents both pass on the imperfect
  recessive gene the birth defect will appear.
• Tay-Sachs and cystic fibrosis are examples of
  such recessive inheritance.

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Errors in Chromosomes

• Can affect the development of the baby
• Several birth defects are caused by problems in
  the numbers or structure of chromosomes.
• An error may occur when an egg or sperm cell is
  developing, causing a baby to have too many or
  too few chromosomes or to have broken or
  rearranged chromosomes.
• These are NOT hereditary defects because neither
  parent has the abnormal chromosome.
• Most common birth defect of this type is Down
  Syndrome. (extra copy of chromosome 21)

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Interaction of Heredity Environment

• Some birth defects are multifactorial, meaning
  they are caused due to environmental and
  hereditary factors
• The baby inherits the tendency for a birth defect
  to occur and is triggered by an external factor.
• Cleft lip and spina bifida may be caused by a
  combination of inherited genes and exposure
  during pregnancy to medications, infections,
  illnesses, and tobacco or alcohol.

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Miscarriage and Stillbirth

• Sometimes a pregnancy begins, but the baby
  doesnt develop normally. In some cases, the
  developing baby dies. If this happens prior to
  the 20th week of pregnancy (month 1-3) the event
  is called a miscarriage. If the baby dies after
  that time, it is called a stillbirth.

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Genetic Counseling

• This is where a specialist evaluates
• the medical histories and family history of both
  individuals, as well as the parents through a
  physical examination.
• they examine other family members, etc.
• They assess the risk of having a child with a
  birth defect that is caused by a defect in the
  genes, if there is a history of a birth defect
  in the family.
• These counselors do not tell people what to do
  they only explain the options and risks.

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Prenatal Tests

• These are tests that are conducted during a
  pregnancy
• Alpha-fetoprotein (AFP)
• Blood test on the expected mother between weeks
  15-20 of pregnancy.
• AFP is a protein produced in the liver of the
  fetus that is detectable in the liver of the
  fetus that is detectable in the mothers blood.
• Abnormal AFP levels can indicate a possible birth
  defect.
• Ultrasound
• Uses sound waves to make a video image of an
  unborn baby.
• Helps the doctor to monitor the development of
  the baby, pinpoint age and detect certain birth
  defects (skeletal, circulatory, nervous system
  defects can be detected in an ultrasound).

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Prenatal Tests

• Amniocentesis
• A sample of the amniotic fluid is withdrawn by
  using an ultrasound to guide a needle through the
  mothers abdomen into the amniotic sac.
• Some cells from the fetus are in the amniotic
  fluid and can be analyzed for defects such as
  Down Syndrome.
• Chorionic villi sampling
• A sample of tissue from the membrane that
  surrounds the fetus is extracted by snipping or
  suction, to check for specific birth defects.
• Detects same defects as amniocentesis, but poses
  a greater safety/health risk to the fetus.