Chapter 4: Prenatal Development

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Chapter 4: Prenatal Development
4.1 The Developing Baby
4.2 Problems in Prenatal Development
4.3 Avoiding Dangers to the Baby
Chapter 4 Objectives
•List the methods of family planning
•Outline what occurs during each of the three stages of prenatal
development
•Contrast miscarriage and stillbirth
•Identify how ten major birth defects can be diagnosed
•Summarize the hazards that alcohol and other drugs pose to prenatal
development
•Assess why environmental hazards must be avoided during
pregnancy
•Describe how a fetus can be affected by certain illnesses the mother
The Developing Baby
Chapter 4 Section 1
Family Planning
Many families carefully consider whether to have children
and when to have them. However, anytime a couple has
sexual intercourse, a pregnancy can occur. The only sure
way to prevent pregnancy is abstinence, or avoiding
sexual activity.
Do you think this statement is true or false?
Conception
 About every 28 days, an ovum (egg) is released by one of a
woman’s two ovaries.
 This is called ovulation; at the same time certain hormones are
released
 During ovulation, the inner lining of the uterus grows and
thickens.
 If the ovum is not fertilized, the lining breaks down and passes
out of the body
 The menstrual period
 When an ovum is released it travels through the fallopian
tube (connects the ovary to the uterus)
 This journey takes about 2-3 days
Conception
 When the ovum reaches the uterus unfertilized, it typically
breaks up
 When a sperm, the male cell, reaches the fallopian tube
it may penetrate and fertilize the ovum
 The process when the sperm fertilizes the egg is called
conception
 Ovum's usually live 12-24 hours while sperm are capable
of fertilizing an ovum for about 48 to 72 hours
 During a woman’s cycle, there are only about 3-4 days in
which conception can occur
Conception
The Role of Genetics
 People inherit many physical traits from their parents
 Skin color
 Hair color and texture
 Eye color
 Size and shape of ears
 Much more…
 Some children are more likely to have talents like musical
talents or athletic ability
The Role of Genetics
 At the moment of conception, every human baby receives
46 chromosomes
 A chromosome is a tiny threadlike structure in the nucleus of
every cell
 Chromosomes come in 23 pairs
 The fathers sperm and mothers ovum contribute 1 to
each pair
 Has hundreds to thousands of gene
 A gene is a unit that determines a human’s inherited
characteristics
 The complete blueprint for the creation of a person is called
a genome
 The complex molecules that make up genes are called DNA
Dominant and Recessive Genes
Dominant
Recessive
 A dominant gene is a
stronger gene
 A recessive gene is a
weaker one and will not be
expressed
•The terms dominant and recessive only refer to the relationship of
genes to each other
•What factor determines the characteristic that a person will express is
the dominant gene
•EX: Red hair genes often skip a generation because the gene is
recessive
•Most traits are influenced by multiple genes
•Height, weight, personality, and intelligence
Let’s Practice
Making a Unique Person
 Heredity explains why people in some families look so
much alike and why some do not
 EX: one child with brown hair and another with bright blond
hair
 The gender of the child is
determined at conception
 Sex chromosomes come in
two types X and Y
 Woman carries the X, and the
man carries the X or Y
1st Month
 At 2 weeks: size of a pin
head
 Egg attaches to the lining
of the uterus
 Critical stage for brain and
spinal cord development
 Internal organs and
circulatory system begin to
form
 The heart begins to beat
2nd Month
 Size about ¼” long at the
beginning of the month
 Face, eyes, ears, and limbs
take shapes
 Bones begin to form
3rd Month
 Size about 1” as the month
begins
 Nostrils, mouth, lips, and
eyelids form
 Buds for all 20 baby teeth
appear
 Fingers and toes almost
complete
 All organs present but still
immature
4th Month
 About 3” long; weighs 1
ounce as the month
begins
 Can suck its thumb,
swallow, hiccup, and
move around
 Facial features become
clearer
5th Month
 About 6 ½’-7” long and
weighs 4-5 oz as month
begins
 Hair, eyelashes, and
eyebrows appear
 Teeth continue to develop
 Organs are maturing
 Becomes more active
6th Month
 Size about 8-10” long and
weighs 8-12 oz. as the
month begins
 Fat deposits under skin, but
fetus appears wrinkled
 Breathing movements
begin
7th Month
 Size about 10-12” long and
weighs 1 ½-2 lbs as month
begins
 Has periods of activity
followed by periods of rest
and quiet
8th Month
 Size about 14-16” long, 2
½-3 lbs as the month
begins
 May react to loud noises
with a reflex jerking action
 Moves into a head-down
position
9th Month

Size about 17-18” long and weighs
about 5-6 lbs as month begins

Weight gain continues

Skin becomes smooth as fat
deposits continue to form

Movements decrease as the fetus
has less room to move around

Acquires disease-fighting
antibodies from the mother’s blood

Descends into pelvis, ready for
birth
Chapter 4 Section 2
Problems in Prenatal Development
Losing a Baby
 Sometimes a baby does not develop normally
 Sometimes the developing baby dies
 Miscarriage is when a baby dies prior to the 20th week of
pregnancy
 Still birth is when a baby dies after the 20th week of pregnancy
 About 15% of recognized pregnancies end in miscarriage
 Causes are still not medically known
 Still birth occurs in about 2% of pregnancies
 Most common causes are problems with the placenta, abnormal
chromosomes, poor growth, and infections
Dealing with Grief
 Most couples feel a long sense of attachment prior to a
baby’s birth
 May go through similar stages of grief that a parent would to
a child that was already born
 Parents may blame themselves and feel alone
 Couples may need support to deal with grief
 Most couples that experience a miscarriage or stillbirth
still have healthy children later
Birth Defects
 A serious problem that threatens a baby’s health, and is
present at birth, is called a birth defect
 Some are mild that no one would ever know the child
has a birth defect
 Others can result in disabilities or even death
 Approximately 120,000 babies are born each year in the
US with a birth defect
 Scientists are still trying to identify some causes
 If found, could possibly decrease the occurrence of birth
defects
Types and Causes of Birth
Defects
 Some defects cause an
abnormality in the structure
of the body
 EX: extra or missing
fingers/toes
 Some defects cause one
or more systems in the
body to not function
properly
 EX: blindness, deafness,
and mental retardation
 Some abnormalities are
not discovered until
months or years after birth
 4 main causes of birth
defects currently:
 Environment
 Hereditary
 Errors in chromosomes
 Combination of
environment and
hereditary factors
Types and Causes of Birth
Defects
Environmental
Hereditary
 Nutritional balance of the
mothers diet
 Parents can pass off faulty
recessive genes
 Any diseases or infection the
mother has
 Harmful substances; alcohol,
over-the-counter medication,
illegal drugs, etc.
 Some medicines help the
mother but hurt the baby
 Air pollution
 Exposure to X-Rays and high
levels of radiation
 This is called recessive
inheritance
 Tay-Sachs disease
 Cystic Fibrosis
Types and Causes of Birth
Defects
Errors in Chromosomes

When a baby has too many or too
few chromosomes

Most common birth defect is Down
syndrome
 1 in 800 children are born with
a form of Down syndrome

When you have too many or too
few it can affect the body’s
systems
 Heart defects
 Leukemia
 Poor muscle tone
 Physical growth or motor
development
Interactions of Heredity
and Environment
 When an environmental and
hereditary factors are
present
 Examples
 Cleft lip
 Cleft palate
 Heredity and
medications
 Spina bifida
 A predisposition,
tendency, are
combined
medications
during pregnancy
Prevention and Diagnosis
 Changing of your lifestyle
 Frequent doctors visits for prenatal check-ups
 Genetic counseling
 Assesses their risk of having a child with a birth defect that is
caused by a defect in genes
 Compiling a family history
 Prenatal Tests
 More than 100 kinds of birth defects can be detected
before birth
Prenatal Tests
Alpha-fetoprotein
(AFP)
 Blood test between 15 and
20 weeks
 AFP is produced in the liver
of the fetus and shows up
in the mothers blood
 Abnormal levels can
indicate a possible birth
defect
Ultrasound
 Is a test that uses sound
waves to make a video
image of an unborn baby
 Can monitor problems with
a baby’s skeletal,
circulatory, or nervous
system
 Usually during their 20th week
 Many doctors now do 3D
ultrasounds
Prenatal Tests
Amniocentesis
 The process of withdrawing a
sample of the amniotic fluid
surrounding the unborn baby
 Often used as a test for Down
syndrome with the mother is
older than 35 years or older
 Also may be completed if
uncertain results are obtained
from the AFP
 Done between the 15th and 20th
week
Chorionic Villi
Sampling
 Uses a sample of tissue
from the membrane that
encases the fetus to check
for birth defects
 Tissue is cut off and
analyzed
Chapter 4 Section 3
Avoiding Dangers to the Baby
Effects of Alcohol and Other Drugs on
Pregnancy
 Essential parts of good prenatal care is avoiding hazards
such as
 Alcohol
 Drugs
 Smoking
 X-Rays
 Hazardous chemicals
 Other harmful substances
 Infections
 Environmental Factors
Alcohol
Fetal Alcohol Syndrome
 Even small amounts can harm
the baby
 Doctors do not know the exact
amount that can harm a baby
 Avoid any amounts when
trying to become pregnant
 Incurable condition found in
some children of mothers that
consumed alcohol during
pregnancy
 1 in 5 babies born with FAS do
not live to 1 year old
 Those that survive can have
problems
 Delayed physical growth
 Heart, liver, kidney defects
 Hyperactivity
 Facial deformity
 Mental retardation
 Learning Disabilities
Alcohol
Fetal Alcohol Effects
 Abnormalities caused by
the mother consuming
alcohol during pregnancy
 Suffer less than children
with FAS
 Extent of damage is
directly related to the
amount the mother drinks
 Binge drinking increases
your risk of having a
child with FAS
Prescription Drugs and Over-TheCounter Drugs
 Extreme example of unsafe mediation is thalidomide
 1950s- to relieve morning sickness
 After proved harmful, 5,000 babies were born with birth defects
 Missing or deformed arms, legs
 Some acne medicine has been proven to cause problems
 Chemicals found in some medications can cause mental
retardation in the first 3 months
 4-9 months, OTC drugs can cause slow growth, infections, and
bleeding at birth
Caffeine
 Passes easily through the
placenta
 Cause high blood levels
of caffeine for fetus
 Increases fetal heart rate
and movement
 Consumed in large amounts:
 Miscarriage
 Premature birth
 Low birth weight
 Can draw fluid and calcium
out of the body
 Small amounts (2 cups of
coffee or soft drinks per day)
not a huge risk
Tobacco
 Cause:
 Low birth weight
 Premature birth
 Linked to:
 Respiratory infections
 Allergies
Illegal Drugs
 Mothers pass their addiction to
their baby
 After birth, babies must go
through a painful period of
withdrawal
 Long-term effects can be
learning and behavioral
disabilities
 Cocaine causes miscarriage, still
birth, and premature births
 Causes unborn child to have
strokes resulting in brain and
heart damage or even
death
 Low birth weight
 Smaller heads
 Risk of seizures
 Risk of SIDS (sudden infant
death syndrome)
 Tremors
 Exaggerated startle response
 Irritability and
developmental delays
 Feeding and sleeping
problems
Illegal Drugs
 Marijuana and
methamphetamine use is
liked to low birth weight
and premature delivery
 Breathing problems
 Poor attention span
 Drowsiness
 Heart defects
Environmental Hazards
 Two possible hazards to unborn babies include X-rays
and hazardous chemicals.
 Radiation from X-rays, or from other sources, can cause
birth defects
 If an X-ray is necessary during pregnancy, inform your
medical staff because precautions can be taken
 Dental X-rays are generally considered safe
Environmental Hazards
 Hazardous Substances and Chemicals
 Paint
 Pesticides
 Lead in water or paint
 Carbon monoxide
 Mercury found in some fish
 Solvents, paint thinners, and formaldehyde
Diseases and Infections
Rubella
Toxoplasmosis
 Rubella is also called the
German measles

Caused by a parasite

Most people have immune systems to
fight it off
 Developing babies cannot

Causes:
 Blindness
 Hearing loss
 Learning disabilities
 Severe cases
 Death
 Long-term learning
disabilities
 Precautions:
 Never clean a cats litter box
 Mother contracts it
 Birth defects can happen
within 1st three months
 Blindness
 Deafness
 Heart disease
 Mental retardation
Diseases and Infections
Chicken Pox
Sexually Transmitted
Infections
 Viral infection
 Passed from mother to baby
 Depending when infection
occurs during pregnancy will
affect the outcome to the baby
 For Example:
 1st half of pregnancy
 Congenital Varicella
Syndrome
 Causes scarring of the
skin, limb defects, eye
problems
 Some cases miscarriage
 Syphilis can be treated if
caught early to the
unborn baby
 Can cause skin rash or
lesions, bone/facial
deformities, deafness,
brain damage
 2% end in miscarriage,
stillbirth, or death

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