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Chapter 5 Section 3 & 4 Birth Defects

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Keri Feight

on 1 May 2018

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Transcript of Chapter 5 Section 3 & 4 Birth Defects

Thank You!
Tay-Sachs Disease
Sickle Cell Anemia
Birth Defects
Chapter 5 Section 3 & 4
A developing baby may die if it does not develop normally
Miscarriage – death of unborn baby before 20 weeks of pregnancy
Stillbirth – death of unborn baby after 20 weeks of pregnancy
Most instances death cannot be prevented and are not caused by any events of the mother or father
20% of all pregnancies end in miscarriage

Losing a Baby

Serious problems that threaten their health or ability to live
Hundred of birth defects; some are mild or can be corrected
Others result in severe lifelong disabilities or even death
3 out of 100 children born in the US have a birth defect

Types of Birth Defects

Birth Defects range from size or shape of the body or body parts
Misshapen foot or an extra or missing finger.
Blindness, deafness, mental retardation
Some birth defects don’t appear for months or years after birth

Birth Defects

About 60% of all birth defects have no known cause.
Research is being done continuously to find the answers
4 main causes of birth defects:
Abnormal genes
Errors in chromosomes
Combination of environment and genetic

Causes of Birth Defects

Each person carries about 5-6 recessive genes that are imperfect. Normally this is not a problem when a single imperfect gene exists but when each parent passes on the same recessive defective gene or an imperfect dominant gene is passed on the baby may develop a birth defect.

Some genetic conditions affect only one sex.

Hemophilia and color blindness only affects males


Most common inherited disease
Problems with breathing and digestion
Many CF die before adulthood; treatment allows those with CF to live longer than in the past
Autosomal Recessive (inherited from both parents) disorder that affects the mucous glands of the body
Symptoms – very salty sweat and a cough that doesn’t go away
Tests can identify carriers of the gene and can diagnose an affected child or fetus
No cure; can be helped with special diets, lung exercises, and treatment
Cystic Fibrosis

Painful blood disorder that often leads to early death; Most common among blacks; malformed red blood cells interfere with the supply of oxygen to all parts of the body
Cause: autosomal recessive gene defect from both parents
When both parents carry the gene their children have a 1 in 4 chance of getting sickle cell anemia
amnio or cvs can identify SCA in fetus; genetic counseling can identify parents who carry the gene; blood tests confirms the presence after birth
No cure; medication treats symptoms
Lack a chemical in the blood that makes their bodies unable to process and use fats. Characterized by a gradual degeneration of the brain that results in blindness and weakening muscles
Children with Tay-Sachs live only a few years at the most
Most common among those whose ancestors came from Jewish communities in Central or Eastern Europe
Autosomal Recessive disorder inherited by both parents
Amnio or CVS for identifying in the fetus; blood test to identify those who carry the defective gene and test for after birth

No cure or treatment
Due to a missing or deficient enzyme, children with PKU cannot process a part of the protein called phenylalanine; following birth children appear normal then by 3-6 months of age they lose interest in their surroundings irritable, restless, destructive, musty odor about hem, dry skin, rashes or convulsions; phenylalanine builds up in the bloodstream and causes brain damage and mental retardation
Autosomal recessive gene defect from both parents
PKU test routinely done shortly after birth
No cure; mental retardation can be prevented if the baby is treated with a special diet that is low in animal proteins (milk, cheese, eggs, meat, fish) and no diet drinks with aspartame (Nutrasweet & Equal)
progressive neurodegenerative genetic disorder that affects muscle coordination & some cognitive functions that become noticeable in middle age
Lack of coordination and unsteady gait
Advance symptoms uncoordinated, jerky body movements; decline in mental abilities and behavioral and psychiatric problems leading to dementia
Autosomal Dominant – only one mutated copy of the gene will be necessary for a person to be affected by this disorder
Affected person usually has one affected parent
50% chance that a child of the affected person will inherit the mutated gene
appearance of physical symptoms
Tests can be performed to confirm the family history of HD prior to family planning
Treatment: drugs available to treat involuntary movement; exercise
Genetic Causes
X linked dominant

developmental problems including learning disabilities and cognitive impairment. Usually, males are more severely affected by this disorder than females.
delayed development of speech and language by age 2.
Most males with fragile X syndrome have mild to moderate intellectual disability, while about one-third of affected females are intellectually disabled.
Children with fragile X syndrome may also have anxiety and hyperactive behavior such as fidgeting or impulsive actions. They may have attention deficit disorder (ADD), which includes an impaired ability to maintain attention and difficulty focusing on specific tasks. About one-third of individuals with fragile X syndrome have features of autism spectrum disorders that affect communication and social interaction. Seizures occur in about 15 percent of males and about 5 percent of females with fragile X syndrome.
Most males and about half of females with fragile X syndrome have characteristic physical features that become more apparent with age. These features include a long and narrow face, large ears, a prominent jaw and forehead, unusually flexible fingers, flat feet, and in males, enlarged testicles (macroorchidism) after puberty.
Fragile X syndrome occurs in approximately 1 in 4,000 males and 1 in 8,000 females.
Fragile X syndrome

Most common form of MD is Duchenne MD; progressive weakness and degeneration of the skeletal muscles that control movement
X-linked recessive; males are affected primarily who inherit the disease from their mothers; females who inherit can be carriers but usually no symptoms; defective gene for dystrophin (protein in the muscles)
generalized weakness and muscle wasting affecting the muscles of the hips, pelvic are, thighs and shoulders; genetic test confirms absence of dystrophin
Testing prior to family planning to determine carriers
steroids for the symptoms; physical activity to help maintain muscle strength, flexibility, braces to improve mobility; respiratory support
Muscular Dystrophy

Bleeding disorder when one of the clotting factors is missing
X-linked recessive genetic defect that usually affects male offspring.
Women who carry the hemophilia gene rarely suffer from the disorder (mutated x chromosome from both parents)
family history of the condition or an abnormal bleeding episode
No cure; regular infusions of the absent clotting factor


X linked recessive
It interferes with the body's ability to break down and recycle specific mucopolysaccharides, also known as glycosaminoglycans or GAG.
GAG builds up in cells throughout the body due to a deficiency or absence of an enzyme (I2S). Buildup interferes with the way certain cells and organs in the body function and leads to serious symptoms. As the buildup of GAG continues throughout the cells of the body, signs of Hunter syndrome become more visible. Physical manifestations for some people include distinct facial features and large head. In some cases,central nervous system involvement leads to developmental delays and nervous system problems. Not all people with Hunter syndrome are affected by the disease in exactly the same way, and the rate of symptom progression varies widely. Hunter syndrome is always severe, progressive, and life-limiting.
*Hunter syndrome

Autosomal recessive:
Cystic Fibrosis, Sickle Cell anemia, Tay-Sachs, PKU,
Autosomal dominant:
Huntington’s Disease
X-linked Dominant:
Fragile X Syndrome
X-linked Recessive:
Muscular Dystrophy (Duchenne), Hunter’s Syndrome, hemophilia


Too many or too few chromosomes in the baby’s cells.
These are not inherited conditions.
Most common is Down Syndrome (Trisomy 21)
1 out of 800 births has this condition.
Risk for this condition increases with the age of the mother
An extra chromosome #21
Each chromosome carries hundreds of genes and having an extra chromosome interferes with development

Errors in Chromosomes

After conception the fertilized ovum has three, not two, number 21 chromosomes. Instead of the 46 chromosomes there are 47
Can be detected by medical tests

Down Syndrome Trisomy 21
Child is short and stocky, often with a heart defect, and is moderately to severely mentally retarded
Older parents have a higher risk than younger parents of having a baby with Down Syndrome
A 35 year old woman has about a one in 350 chance of conceiving a child with Down syndrome, and this chance increases gradually to 1 in 100 by age 40. At age 45 the incidence becomes approximately 1 in 30.
No cure for Down Syndrome
Educational training can help those with the disorder lead more normal lives.
Severe mental retardation, health problems related to every organ system in the body; 90% of babies born with Tri 13 or 18 die by age 1; 5-10% survive the first year of life; babies appear frail problems feeding
Errors during meiosis (production of sex cells) or translocation
Amnio prenatally; blood test after birth
Treatment: No cure & no treatment

Trisomy 18 Trisomy 13 Trisomy 5
*Trisomy 13 (Patau Syndrome)/18 (Edwards syndrome)

XXY condition; only affects males (extra X chromosome)
Physically weaker muscles and reduced strength- delayed motor skills
Less testosterone; larger breasts, less facial hair and body hair, broader hips, weaker bones, lower energy level than other males
Autoimmune disorders, breast cancer, vein diseases, tooth decay little to no sperm production (infertile)
An extra X chromosome in most cells
May not be diagnosed until a man goes in for infertility problems; semen count; karyotyping; blood test

Klinefelter’s Syndrome

Turner Syndrome

all or part of one of the sex chromosomes is absent 
characteristic physical abnormalities, such as short stature, swelling, broad chest, low hairline, low-set ears, and webbed necks
Girls with Turner syndrome typically experience gonadal dysfunction (non-working ovaries), which results in amenorrhea (absence of menstrual cycle) and sterility. Concurrent health concerns may also be present, including congenital heart disease, hypothyroidism (reduced hormone secretion by the thyroid), diabetes, vision problems, hearing concerns, and many autoimmune diseases
a specific pattern of cognitive deficits is often observed, with particular difficulties in visuospatial, mathematical, and memory areas.

*Prader-Willi Syndrome

Very rare
seven genes (or some subset thereof) on chromosome 15 are deleted or unexpressed
low muscle tone, short stature, incomplete sexual development, cognitive disabilities, problem behaviors, and a chronic feeling of hunger that can lead to excessive eating and life-threatening obesity

Examples are:
Heart defect, cleft lip/cleft palate, spina bifada

A child may have a tendency for a specific birth defect and the defect may appear if some factor (Virus or drug) affects the baby during development

Combination of Environment & Heredity

Description: a gap in the upper lip or palate; causes problems with eating, swallowing, speech, and appearance
Associated problems include dental (missing teeth, malformed or displaced teeth and cavities, ear infections
Causes: Combination of genetic and environmental factors (drugs, illness, use of alcohol/tobacco during pregnancy)
Detection: apparent at birth;
ultrasound prior
Treatment: Surgery to correct the
gap thus eliminating the
problems that go with it

Cleft lip/palate

Description: Bones of the spinal column do not close completely around the developing nerves of the spinal cord; spinal cord may stick out through an opening in the spine leading to permanent nerve damage; neural tube fails to close completely during the first few weeks of embryonic development
Causes: Combination of genetic and environmental factors (shortage of folate/folic acid/B vitamin; obesity, diabetes, exposure to high heat, use of anti-seizure meds during pregnancy)
Detection: apparent at birth, amniocentesis, ultrasound
Treatment: corrective surgery, physical therapy

Spina Bifada

*Multiple Sclerosis
Damage (lesions) on the brain and spinal cord that cause damage to the covering that protects nerves and promotes the efficient transmission of nerve impulses
Sensory disturbances begin in adulthood (20-40); blurred vision, red-green distortion; muscle weakness and difficulty with coordination and balance; fatigue progressive
Cause: combination of genetics and environment (exposure to Epstein-Barr virus, low levels of Vitamin D, and smoking)
*Tourette’s Syndrome
Characterized by repetitive, sudden, and involuntary movements/noises (tics)
Rapid eye blinking, shoulder shrugging, nose twitching, grunting, sniffing, throat-clearing
Genetic & environmental


During the zygote and embryo stage the baby develops all the bodily systems needed for survival. All the nourishment and oxygen the developing baby receives comes from the mother’s body. So, the decisions the mother makes and the conditions of the mother can affect the development of her baby.

Environmental causes

Nutritional balance of mom’s diet
Diseases or infections of the mother during pregnancy
Harmful substances (alcohol, tobacco, drugs) taken during pregnancy
Medications that benefit the mother but may hurt the baby
Exposure to outside hazards like radiation early in pregnancy
Examples of infections that can cause birth defects are rubella (German measles), cytomegalovirus (CMV), syphilis, toxoplasmosis, Venezuelan equine encephalitis, parvovirus, and, rarely, chicken pox. None of these infections affect 100% of babies whose mothers are infected during pregnancy. If the mother is infected during early pregnancy, rubella carries the highest risk for birth defects - approximately 20%.

Environmental includes

Description: Problems of the motor system; lack of coordination, stiffness, jerkiness, difficulty with speech and paralysis
Causes: damage to the brain before, during, or shortly after birth
Detection: symptoms appear in the 1st year of life
Treatment: damage to the brain is irreversible; physical therapy, speech therapy, medication can treat some problems

Cerebral Palsy

Radiation from x rays or other sources can cause birth defects
Take special precautions if x rays need to be taken
X-rays can cause problems with fetal development, such as spina bifida, cleft palate, blindness, abnormalities of the arms and legs, or microcephaly, which is a condition where the brain is too small. The type of abnormality that develops depends on the dose of X-ray radiation the pregnant woman receives, and how far along the pregnancy is. There is no established safe dose of X-ray radiation. However, dental X-rays (and dental cleanings) are considered safe during pregnancy. Talk to your caregiver if you are asked to have an X-ray and you are pregnant or you think you could be pregnant.

Radiation and chemotherapy, which are used to treat cancer, are also associated with congenital abnormalities. If at all possible, the use of radiation and chemotherapy should be delayed until after the baby has been delivered. Sometimes this is not possible, however, and the risks of these treatments must be weighed against their benefits to the mother.
X Rays

Nicotine in cigarettes – drug
Linked to:
premature birth
Low birth weight
Respiratory infections


A developing infant can be infected with AIDS by the mother
A woman who is pregnant should be tested for AIDS so she can be given treatment that can reduce the chances that her baby will develop AIDS


Many STDs can be passed from the mother to the developing child
Can result in serious illness, deformity or death
Can carry an STD without knowing it and transmit without knowing it
Doctors routinely test pregnant women for syphilis and required by law in many states
Doctors treat the eyes of newborns with a solution to kill gonorrhea germs that could cause blindness
No drug can cure the damage to the newborn that results from a delay in diagnosis & treatment


German measles
During pregnancy if the mother is exposed to rubella she may never show symptoms but the developing baby could suffer
Heart disease
Mental retardation
Vaccination for rubella should not be given during pregnancy or if a woman plans on becoming pregnant soon after


Coffee, tea, cocoa, soft drinks
Problems associated with large amounts of caffeine:
Increased risk of miscarriage
Low birth weight
Higher rates of infant death


No completely safe drug
Taken in the 1st trimester can result in developmental defects of the brain; taken in the 2nd & 3rd trimester can slow growth, cause infection, or bleeding during birth
Caused more than 5,000 babies to be born with severe birth defects
Medicines or infections
that reach the developing
baby in the 1st 3 months of
pregnancy have the most
devastating effect.
History of Thalidomide in pictures CNN
History of Thalidomide & FDA in the US

Prescription/Over the counter Meds

Drugs pass the placenta and cause addiction on to the baby
Lifelong effects
Infants will go through withdrawal – painful condition resulting from the body no longer receiving the drug that it depends on
Withdrawal can lead to infant death
Long-range effects on the infant are the inability to follow simple directions
Cocaine can cause miscarriage, stillbirth, premature birth, birth defects
1960s LSD was proposed for use in the treatment of neuroses

Illegal drugs

1 in 5 babies born with FAS dies soon after birth
Survivors suffer from many problems
Growth & development
Slow growth, poor coordination, heart defects, facial disfigurement, learning problems & hyperactivity
No cure for FAS or FAE
Less severe condition with some of the damage
100% preventable
No known amount that results in FAS or FAE – so avoid alcohol completely during pregnancy


Some birth defects can be prevented. Those caused by infections, drugs, &/or alcohol can be controlled
To minimize the possibility of birth defects parents need to make healthy choices.

Others cannot be prevented but tests can be done to determine the likelihood of a child developing a birth defect so treatment can be done ASAP

Prevention and Diagnosis of Birth Defects

Expert information and explanation about heredity, especially about the risk for disorder to be passed along to children through the genes
genetic counselor has a masters degree in genetic counseling and has studied genetic diseases and how those diseases run in families. The genetic counselor can help a person or family understand their risk for genetic conditions (such as cystic fibrosis, cancer, or Down syndrome), educate the person or family about that disease, and assess the risk of passing those diseases on to children.
A genetic counselor will often work with families to identify members who are at risk. If it is appropriate, they will discuss genetic testing, coordinate any testing, interpret test results, and review all additional testing, surveillance, surgical, or research options that are available to members of the family.

Genetic Counseling

Through prenatal testing more than 100 kinds of birth defects can be diagnosed before birth
Prenatal testing can alert physicians to conditions that must be treated before or immediately after birth
Blood tests
Amniocentesis – 15th – 18th week of pregnancy
could cause a miscarriage (less than 1%, or approximately 1 in 200 to 1 in 400)
Injury to the baby or mother, infection, and preterm labor are other potential complications
Chorionic villi sampling CVS -10 to 12 weeks of pregnancy
risks of CVS are only slightly higher than those of an amniocentesis
Possible complications
Rh incompatibility in the mother
Rupture of membranes
Some of these tests can be risky while providing valuable information
May be harmful to the developing fetus

Prenatal Tests

Sound waves to make a video image of an unborn baby to check for specific health problems
usually done during the second trimester of pregnancy, when the woman is about 18 – 24 weeks pregnant.
The procedure is similar to that of a pregnancy ultrasound. You will lie down for the procedure.
The test can be performed on your belly (abdominal ultrasound) or through your vagina (transvaginal ultrasound).
In an abdominal ultrasound, the person performing the test places a clear, water-based gel on your belly and then moves a hand-held probe over the area. The probe sends out sound waves, which bounce off the baby’s heart and create a picture of the heart on a computer screen.
In a transvaginal ultrasound, a much smaller probe is placed into the vagina. A transvaginal ultrasound can be done earlier in the pregnancy and produces a clearer image than an abdominal ultrasound.
Helps determine if the baby is developing on schedule
Confirm due date or multiple births
Virtually no risk to mother or baby


Amniocentesis removes a small amount of fluid from the sac that surrounds the baby in the womb (uterus).
You will probably have a pregnancy ultrasound first. This helps find out exactly where the baby is in your womb.
Numbing medicine is then rubbed onto part of your belly.
the medicine is given through a shot in the skin on the belly area.
The health care provider inserts a long, thin needle through your belly and into the womb.
A small amount of fluid (about 4 teaspoons) is removed from the sac surrounding the baby.
The fluid is sent to a laboratory, where:
Genetic studies are done.
Can be done between 14-20 weeks. Some facilities will perform the test as early as 11 weeks.

Other tests may be done.

Used to test for Down Syndrome in women over 35 & done if you
Have had babies with birth defects in previous pregnancies.
Have a family history of genetic disorders
1 in every 200 women who have had amniocentesis have a miscarriage
Only performed when a strong medical reason
amniocentesis slideshow


CVS can be done through the cervix (transcervical) or through your  belly (transabdominal). Miscarriage rates are slightly higher when the test is done through the cervix.    
The transcervical procedure is:
inserting a thin plastic tube through the vagina and cervix to reach the placenta
uses ultrasound images to help guide the tube into the best area
removes a small sample of chorionic villus tissue.
The transabdominal procedure is:
inserting a needle through the abdomen and uterus and into the placenta
Ultrasound is used to help guide the needle
small amount of tissue is drawn into the syringe
The sample is placed in a dish and evaluated in a laboratory. 
Used for similar conditions as amniocentesis but can be done earlier in pregnancy (10 to 12 weeks of pregnancy)
Risks of CVS are miscarriage and birth defects and these risks are greater than those of amniocentesis
Done only after careful consideration of the medical reasons and risks
CVS Slideshow


Autosomal – not one of the sex chromosomes
Autosomal dominant – inherited from one parent who is affected; 50% chance of passing it on to his/her offspring; either sex
Autosomal recessive – both parents carry the trait and the offspring receives the nonfunctional gene from each; 25% chance of inheriting the disorder and having symptoms; 50% chance of receiving a defective gene and being a carrier with no symptoms; 25% chance of not having the disorder and not being a carrier; see chart below *
X-linked dominant – affected fathers will transmit the disorder to only daughters; affected mothers will have a 50% chance of transmitting the disorder to offspring
X-linked recessive – typically only affects males; nonaffected female is a carrier who will pass on the disorder to 50% of sons and 50% chance daughters will be carriers; affected male, all daughters will be carriers

Umbilical Blood Sampling
examines blood from the fetus to detect fetal abnormalities
Guided by ultrasonography to determine the location of where the umbilical cord connects to the placenta, the doctor then inserts a needle through the abdominal wall and uterus into the umbilical cord. A sample of the fetus’s blood is withdrawn from the cord and analyzed.
results within 72 hours
similar procedure to amniocentesis but taking cord blood instead of amniotic fluid
This test is used to check for fetal anemia
Can be performed after 17 weeks
is usually done when diagnostic information can not be obtained through amniocentesis, CVS, or ultrasound, or if the results of these tests were inconclusive.
umbilical blood sampling is an invasive procedure. It may cause miscarriage in about 1 in 100 procedures.
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