Transcript PPT Presentation on development

Prenatal Development & Birth
Conception & Genetics
• When does life begin?
• Process of Conception:
– Every 28 days egg is
released, which contains 23
chromosomes
– Gametes – cells that have
only 23 chromosomes.
• Rx indicates that only about
half of all conceptions are
likely to survive to birth.
What are some reasons for
this large number of
fertilized eggs not
surviving?
• Male gamete + female
gamete = zygote
Conception
Two Types of Chromosomes:
• 22 of the pairs of
chromosomes are called
autosomes
• Sex chromosomes = X or Y
– Female has two X
chromosomes (XX)
– Male has one X and one Y
– Gender of a child is
determined by the sex
chromosome from the sperm
(because mom only has X
chromosomes)
• Chromosomes are comprised
of DNA (deoxyribonucleic acid)
that is further subdivided into
genes.
Twins: Identical
Monozygotic Twins
• Aka= identical twins
• A single egg is fertilized to form one zygote
which then divides into two separate
embryos.
• Odds of having identical twins are about 4 in
1,000
• Same sex (gender)
Twins: Fraternal
Dizygotic Twins
• Aka = fraternal twins
• Two eggs are fertilized by two separate sperm.
• Same sex or opposite sex
– Number of multiple births has increased 65% over
last 25 years
• Women 35+ more likely to conceive twins & other multiples
• Women 35+ are more likely to be treated with fertility drugs
Genetics
• Genotype – specific genetic material on an
indiv’s chromosomes.
• Phenotype – the observed characteristic of
the indiv (brown eyes; blonde hair)
DOMINANT AND RECESSIVE CHARACTERISTICS
Characteristics in the left-hand column dominate over those characteristics listed in the right-hand colum
DOMINANT TRAITS
RECESSIVE TRAITS
eye coloring
brown eyes
grey, green, hazel, blue
eyes
vision
farsightedness
normal vision
normal vision
normal vision
normal vision
nearsightedness
night blindness
color blindness*
hair
dark hair
non-red hair
curly hair
full head of hair
widow's peak
blonde, light, red hair
red hair
straight hair
baldness*
normal hairline
facial features
dimples
unattached earlobes
freckles
broad lips
no dimples
attached earlobes
no freckles
thin lips
Immunity to poison ivy
Normal hearing
Normal blood clotting
Normal pigmented skin
Susceptibility to poison ivy
Congenital deafness
Hemophilia
albinism
Other
* sex-linked characteristic
Polygenic Inheritance
• Many genes influence the phenotype.
• controlled by more than one gene, ie. height,
weight, hair color, skin color (basically
anything dealing with color).
Multi-Factorial Traits
• Physical traits influenced by both genes and
environment.
– Height is an example: If a child is ill, poorly
nourished, or emotionally neglected, s/he may
be smaller than others her/his age.
– Psychological traits (intelligence, personality)
influenced by both nature and nurture (multifactorial)
Pregnancy
In the Beginning…
Nine months?
• Pregnancy begins when
the zygote (male
gamete + female
gamete) implants itself
in the lining of the
woman’s uterus.
• Zygote send chemical
messages for
menstruation to stop.
Twenty weeks…
•the uterus can be
felt at the level of
your bellybutton
•As a result, the
pelvic colon and
small intestines are
crowded upward and
backward.
The end!
•
40 weeks
• Common
discomforts you may
experience during the
last weeks of
pregnancy are
frequent urination,
increased
constipation, edema
(water retention), and
aching of the legs
Prenatal Development
Developmental Principles:
• Cephalocaudal pattern –
causes dev’t to proceed
from the head down.
• Proximodistal pattern –
causes dev’t to happen in
an orderly way from the
center of the body outward
to the extremities.
Three Stages of Prenatal
Dev’t:
1. Germinal Stage
2. Embryonic Stage
3. Fetal Stage
Germinal Stage
• First two weeks of gestation,
from conception to
implantation = germinal stage
• During first 24-36 hours after
conception cell division begins
• Cells are alike until @ 4 days
after conception; they form a
hollow sphere with two layers
= blastocyst.
• Placenta = organ that allows
oxygen, nutrients and other
substances to be transferred
between mom and baby’s
blood. (Brings mother’s and
baby’s blood close to one
another without allowing them
to mix.)
• Blastocyst’s inner cells begin to
specialize
– Umbilical cord – connects the
embryo to the placenta
– Aminion – fluid-filled sac in
which baby floats
Embryonic Stage
• Begins when
implantation is
complete (@ 2nd week)
• Ends at week 8
• Embryo’s cells start to
specialize to form
body’s organs (aka:
organogenesis)
Fetal Stage
• Beginning at week 8 and
ending at birth
• Weight increases from onefourth ounce to 7-8 pounds
• Height increase from one
inch to 20 inches
• Nervous system dev’t
• Viability = baby’s ability to
live outside the womb (@
22 weeks)
Gender Differences
• Male fetuses tend to be
more physically active
than female fetuses
• Male embryo secretes
the male hormone
testosterone
• Female fetuses tend to
be more sensitive to
external stimulation
and advance more
rapidly in skeletal dev’t
• Boys are more
vulnerable to prenatal
probs (spontaneous
miscarriage; birth
defects)
Prenatal Behavior
• 25th week, fetus responds
to sounds and vibrations
with heart rate changes,
head turns and body
movements.
• Neonates appear to
remember stimuli to which
they were exposed
prenatally—their mother’s
heartbeat, the odor of
amniotic fluid…
• Very active fetuses tend to
become children who are
very active
• Fetuses who are less active
than “average” are more
likely to be developmentally
delayed.
Genetic Disorders
• Autosomal Dx
– Caused by genes located on
the autosomes.
– i.e., phenylketonuria (PKU)
= involves a recessive gene
that causes a baby to have
prob’s digesting the amino
acid phenylalanine. Can cause
MR as the toxins build up in
baby’s brain. More likely to
occur in Caucusian babies.
– Sickle-cell disease =
recessive dx that causes red
blood cell deformities. Blood
can’t carry enough oxygen to
keep the body’s tissues
healthy. More common in
West African and AfricanAmerican infants.
– Huntington’s disease =
caused by dominant genes
and not usually diagnosed
until adulthood. Causes the
brain to deteriorate and
affects psychological and
motor functions.
Genetic Disorders
• Sex-Linked Dx’s
– Most sex-linked dx’s are
caused by recessive genes
– i.e., red-green color
blindness = people have
difficulty distinguishing
between the colors red and
green when they are next to
each other.
– Hemophilia = the blood
lacks the chemical
components which cause the
blood to clot.
– Fragile-X syndrome =
person has a “fragile” or
damaged spot on the X
chromosome. Can cause MR
that becomes progressively
worse as children age.
– What if parents find out their
baby has a genetic dx?
Should this information
influence their decisions?
Chromosomal Errors
• Chromosomal errors =
Probs that occur when a
child has too few or too
many chromosomes
• Trisomies = a condition in
which a child has three
copies of a specific
autosome.
– Most common is trisomy 21
or Down syndrome (3
copies of chromosome 21)
• Sex-Chromosome Anomalies
= anomalies associated with
the sex chromosomes
– Klinefelter’s syndrome –
XXY pattern. Affected boys
usually look normal but
have underdeveloped
testes and a sparsity of
sperm. At puberty, they
experience both male and
female changes.
Prenatal Influences on Development
• Environmental factors –
– Teratogens –
environmental stimuli
harmful to developing fetus
• Diseases during pregnancy
– any disease that can cross
the placenta
– German measles = minor
effects on mother, major
effects on fetus (blindness,
deafness, heart disease)
– Genital herpes & AIDS=
can cross placenta
• Drugs – legal & illegal
– Caffeine = can slow fetal
growth & contribute to
premature birth
– FAS = abnormally small
head, irritability,
hyperactivity & retarded
motor development and
cognitive development
Other Maternal Influences on Prenatal
Development
• Diet
– Inadequate nutrition may
result in premature birth and
low birth weight
– Folic acid – need adequate
amounts; inadequate amounts
can result in diseases such as
spina bifida
• Age
– Societal shift = older mothers
– Older mothers = higher risk
for genetic abnormalities,
miscarriage & stillbirth
– What about older fathers?
• Maternal Emotions
– Studies show extreme
maternal stress is associated
with low birth weight and
premature births.
• Environmental Hazards
– Lead, mercury, x-rays
– Effects may include mental
disability, retarded growth,
impaired memory and verbal
skill, and leukemia.
Prenatal Diagnosis and Treatment
• Genetic Counseling
– Helps to assess the chances of inherited disorders.
• Prenatal Diagnosis
– Ultrasound is the use of soundwaves to produce a
picture of the fetus.
– Amniocentesis allows the taking of a sample of the
amniotic fluid.
– Chorionic Villus Sampling (CVS) is taken from the
placenta and can be done earlier than amniocentesis.
Prenatal Diagnosis and Treatment
(cont.)
• Fetal Medicine
– Administering medicine to the fetus.
– Fetal Surgery to correct spina bifida and
circulatory problems.
– Genetic Engineering involves replacing
defective genes with synthetic normal genes.
Birth: The Final Push
• Labor and Delivery
• What are the different phases of labor and
delivery?
• What are “natural” ways of coping with the
pain of childbirth? Is childbirth at home
safe?
• What are some complications that can occur
during birth?
Labor and Delivery
• Stages of Labor
• Stage 1 lasts 12-24 hours for the first birth
and includes contractions and the
enlargement of the cervix to approximately
10 centimeters.
• Stage 2 includes the actual birth of the baby
and lasts about an hour.
• Stage 3 lasts a few minutes and involves
expelling of the placenta.
Labor and Delivery
• Approaches to Childbirth
• Childbirth Classes
– Explains what happens during pregnancy and
delivery.
– Teaches techniques to manage the pain of
childbirth. The emphasis is on natural
methods, relaxation, and coaching.
– Studies show that mothers who attend
childbirth classes typically use less
medication.
Labor and Delivery
• Approaches to Childbirth
• Birthing Alternatives
– Home Births
• Less Expensive
• Parents have more control over the conditions
• Birth problems are no more common at home than
at the hospital when pregnancy has been problemfree.
– Birthing Centers
• More home-like than hospitals, but in a clinic
setting independent of hospitals.
Labor and Delivery: Birth Complications
• Hypoxia, or inadequate
blood and oxygen to
baby.
• Complications may
result in cesarean
section (C-section)
• Births before the 36th
week are called
premature or preterm.
• Babies weighing less
than 5.5 pounds have
low birth weight.
• Babies weighing less
than 3.3 pounds have
very low birth weight.
• Below 2.2 pounds is
called extremely low
birth weight.
Thailand. 18.23
Labor and Delivery
• Infant Mortality
• Infant Mortality is the number of infants out of
1,000 births that die before the age of 1 year.
• Thailand mortality rate is about 2%, or. 18.23 of
1000.
• Possible factors include low birth weight resulting
from a lack of free or inexpensive prenatal care and
fewer paid leaves of absence for pregnant women.
Apgar Test
Sign
0
1
2
Heart Rate
Absent
<100 beats/min
100-140
beat/min
Respiratory
Effort
No breathing for
1 min
Slow and
irregular
Good respiration
normal crying
Muscle Tone
Limb and flaccid
Some flexion of
extremities
Good flexion and
active motion
Reflex
Irritability
No facial
expressions
Some
contortions and
grimacing
Active crying
Body color
Blue or pale
body/
Extremities
Body pink w/blue Pink all over
extremities