???? Birth Defects

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???? Birth Defects
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• Birth defects are defined as
  abnormalities of structure, function, or body
  metabolism that are present at birth.

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1. General

• One of the most common worries for
  expectant parents is that something will be wrong
  with their baby.

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• Understanding the nature and causes of
  birth defects can help reduce the mystery, fear
  and guilt often associated with them.

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• However, most babies are born without
  problems, while most of those who are can have
  treatment that will make them much better, or
  even allow them to lead a normal life.

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• An international monitoring programme
  shows that, across Europe, just over 2 per cent
  of babies are discovered at birth to have a
  defect that will affect their ability to survive
  or function normally.

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• Some defects are often not discovered
  until later (eg deafness and problems in
  walking).

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• There is considerable regional variation
  in the rate of defects seen at birth. Glasgow and
  Dublin have traditionally been black spots, with
  rates over 3 per cent, but these figures are
  falling.

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• The number of babies actually born with
  defects is also markedly affected by the
  availability of prenatal screening, and the
  availability of voluntary termination of
  pregnancy in the case of severe abnormalities.

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2. Forms of Birth Defects

• Defects of limbs, heart and spinal cord
  represent about half of all abnormalities.

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• The most common kinds of defect are
  those affecting the limbs (arms and legs). These
  include missing or extra fingers or toes,
  deficiencies in limb length, and abnormalities in
  positioning, such as club foot.

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• Heart abnormalities represent the next
  most common category of defect. Common heart
  defects include 'holes in the heart' where blood
  can pass from one side of the heart to the other.
  Again, these may not all be detected at birth.

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• The third most common kind of defect
  affects the spinal cord, such as spina bifida.

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• Other defects commonly observed include
  those affecting the face (such as cleft lip and
  palate), problems with the development of the
  intestines and stomach, and problems affecting
  the sexual organs.

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Single gene disorder

• Ploygene disorder

• Chromosome disorder

• Mitochondrial disease

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• Major chromosomal problems such as Down's
  syndrome (Trisomy 21) are found in about 0.15 per
  cent of births (about three babies in every
  2000).

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3.The cause of birth defects

• In ancient times, abnormalities were seen
  as warnings or punishments from the gods. Even
  quite recently, it was believed that specific
  events during the pregnancy - such as being
  frightened by a mouse - would lead to specific
  defects in the baby, eg a mouse shaped birth
  mark. Such folk beliefs still persist in places.

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• A. Genetics
• Genetics play a role in birth defects.
  One missing or faulty gene can cause a birth
  defect.
• gene mutation
• Chromosome aberration

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• It may be that they are carriers of the
  condition, or that the genetic problem occurred
  for the first time in the cells that gave rise to
  the baby. Known genetic causes account for about
  25 per cent of all abnormalities.

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• B. Environment Environmental causes
  (including exposure to drugs, radiation and
  illnesses) can be identified in about 10 per cent
  of birth defects. The risk of exposure to such
  environmental factors often causes great concern,
  although genetic causes are more common.

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• There are three main kinds of factor
  that can cause defects chemical, biological and
  physical.

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• Chemical factors, including drugs
  Thalidomide is perhaps the most notorious example
  of a drug that caused defects. It was brought on
  to the market after inadequate testing and
  specifically prescribed for pregnant women.

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• Treatment for pregnancy reaction
• untoward effectsdefect of limbs(
• phocomelia)

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• Following this, much stricter rules about
  drug testing were introduced, and international
  monitoring programmes were put in place. Doctors
  are also much more cautious about prescribing
  drugs to women of child-bearing age, so it is
  unlikely that a disaster on this scale will occur
  again in the UK.

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• Several medical treatments pose the risk
  of birth abnormalities.
• Tetracycline(antibiotic) affect hard tissue
  formation during the foetal period, affecting the
  long bones and teeth.

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• Some anticonvulsant medicines used for
  epilepsy may also cause problemshare lip, limbs
  defects, congenital heart disease

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• Moderate alcohol use in pregnancy is a
  particularly tricky problem.

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• Smoking is bad for the development of
  the baby in a number of ways. Pregnant women
  should not smoke under any circumstances.

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• Lack of something may be as damaging as
  the presence of something. Extensive trials have
  confirmed that taking folic acid before pregnancy
  can reduce the number of spinal cord defects such
  as spina bifida.

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• poisons pollution

Cri du chat syndrome
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• Biological factors, including illnesses The
  rubella virus, which causes German measles, poses
  a serious hazard to the developing baby. It can
  cross the placenta and attack the baby to cause a
  range of defects.
• The proportion of mothers infected with
  the rubella virus during the first 12 weeks of
  pregnancy who have an abnormal child can reach 20
  per cent.

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• cytomegalovirus also cause problems as
• Enlarged spleen
• Liver problems
• Jaundice (yellowing of the skin and eyes)
• Small size
• mental retardation,
• cerebral palsy
• vision and hearing loss

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• herpes simplex
• 4weeks 61
• 5-8weeks 26
• 9-10weeks 6
• Heart defects deafness cataract

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• Bacteria such as salmonella, present in
  undercooked meat (especially chicken), and
  listeria (found in some cheeses), can cause
  problems for the continuation of the pregnancy
  (rather than birth defects).

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• Toxoplasma
• Toxoplasma is a species of parasite
• The definitive host of the cat, but the parasite
  can be carried by many warm-blooded animals .
• Toxoplasmosis, the disease of which T. gondii is
  the causative agent, is usually minor and
  self-limiting but can have serious or even fatal
  effects on a fetus whose mother first contracts
  the disease during pregnancy.

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• Acute stage Toxoplasma often give flu-like
  symptoms in the early acute stages
• The acute stage fades in a few days to months,
  leading to the latent stage. Latent infection is
  normally asymptomatic but some induce
  encephalitis, which can be deadly
• If infection occurs for time during pregnancy,
  the parasite can cross the placenta, possibly
  leading to hydrocephalus or chorioretinitis.

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• Physical factors (including radiation)
  X-rays and radiation given as cancer therapy can
  affect the baby. Your medical carers will be very
  cautious about giving you an abdominal X-ray if
  you are pregnant or potentially pregnant (this
  means almost every woman of child-bearing age!).

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• C. Other factors The exact causes of the
  remaining 65 per cent of defects are currently
  unclear. Many of these defects arise from an
  interplay of genetic and environmental factors.

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4. When a baby most vulnerable

• The time at which the developing baby is
  exposed to a possibly damaging environmental
  factor is more important in determining the
  nature of the likely abnormality than the nature
  of the factor itself.

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• In fact, if babies are exposed to the same
  damaging factor at different times in their
  development, the nature of the damage is likely
  to be different.

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• For instance, exposure to the rubella
  virus at three weeks after fertilisation may
  cause heart defects, and at six weeks after
  fertilisation, it may cause deafness. Exposure
  radiation at three weeks may cause similar damage
  to rubella.

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'sensitive period
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• Pregnancy is usually timed from the last
  menstrual period, which is generally about a
  fortnight before fertilisation. Three weeks after
  fertilisation to the '10th week of pregnancy'.

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• The developing baby is particularly
  vulnerable to environmental factors during a
  five-week period starting about three weeks after
  fertilisation, and lasting till about the end of
  the eighth week after fertilisation.

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5. Spina Bifida

• Spina bifida is a birth defect that
  involves the incomplete development of the spinal
  cord or its coverings. The term spina bifida
  comes from Latin and literally means "split" or
  "open" spine.

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• caused by the incomplete closure of the
  embryonic neural tube.

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• A. Types of Spina Bifida
• The causes of spina bifida are largely
  unknown. Some evidence suggests that genes may be
  involved. A high fever during pregnancy may
  increase a woman's chances of having a baby with
  spina bifida. Women with epilepsy who have taken
  the drug valproic acid may have an increased risk
  of having a baby with spina bifida.

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• Spina bifida occurs at the end of the
  first month of pregnancy when the two sides of
  the embryo's spine fail to join together, leaving
  an open area. In some cases, the spinal cord or
  other membranes may push through this opening in
  the embryo's back. The condition can typically be
  detected before a baby is born and treated right
  away.

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neural tube
coccyx end
Head end
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spina bifida occulta
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• The vertebrae are not completely closed. The skin
  at the site of the lesion may be normal, or it
  may have some hair growing from it.
• Many people with the mildest form of this type of
  spina bifida do not even know
• Back pain.

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• meningocele

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12345 Spinous process Central canal Skin partially covering the neural tube defectSpinal cordDura mater
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• the meninges are forced into the gaps between the
  vertebrae.
• As the nervous system remains undamaged,
  individuals with meningocele are unlikely to
  suffer long-term health problems, although there
  are reports of tethered cord.

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• The protruded portion of the spinal cord and the
  nerves which originate at that level of the cord
  are damaged or not properly developed. As a
  result, there is usually some degree of paralysis
  and loss of sensation below the level of the
  spinal cord defect. Thus, the higher the level of
  the defect the more severe the associated nerve
  dysfunction and resultant paralysis

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myeloschisis (rachischisis)
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• 1 Spinous process 2 Spinal cord 3 Dura mater
  4 Skin up to the neural tube defect

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• occurs when the spinal canal and backbone do not
  close before birth, causing the spinal cord to
  protrude through an opening in the back. This can
  cause partial or complete paralysis below the
  spinal opening.
• Patients have loss of function of lower
  extremities and may also have bowel and bladder
  dysfunction.

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• Arnold-Chiari malformation

the medulla oblongata
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anencephalus
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• occurs when the cephalic (head) end of the neural
  tube fails to close
• resulting in the absence of a major portion of
  the brain, skull, and scalp.
• Children with this disorder are born without a
  forebrain, the largest part of the brain
  consisting mainly of the cerebral hemispheres
• The remaining brain tissue is often exposednot
  covered by bone or skin

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END