Download prenatal & Birth

3. Prenatal Development and Birth
Have you ever thought about what an absolute
miracle your life is?
You began with two microscopic cells and NOW
look at you! You are trillions of cells all working
together to allow you to sit up, read, feel, digest,
and even, when the time is right, make a miracle of
your own.
Development begins with conception.
Conception occurs when fertilization
creates a zygote, a one-celled organism
formed by the union of sperm and an
egg. All of the other cells in the human
body develop from this single cell.
Prenatal development is the process in which an
embryo or fetus gestates during pregnancy, from
fertilization until birth.
The Course of Prenatal Development
The prenatal period is divided into three phases:
1. Germinal Stage
This brief stage begins when a zygote is created through
fertilization. Within 36 hours, rapid cell division begins,
and the zygote becomes a microscopic mass of multiplying
cells. This mass of cells slowly migrates along the mother’s
fallopian tube to the uterine cavity. On about the seventh
day, the cell mass begins to implant itself in the uterine
wall.
2. Embryonic Stage
During this stage, most of the vital organs and bodily
systems begin to form in the developing organism, which is
now called an embryo. Structures such as the heart, spine,
and brain emerge gradually as cell division becomes more
specialized.
Although the embryo is typically only about an inch long at
the end of this stage, it’s already beginning to look human.
3. Fetal Stage
The developing organism, now called a fetus, becomes
capable of physical movements as skeletal structures harden.
Organs formed in the embryonic stage continue to grow and
gradually begin to function. Sex organs start to develop
during the third month.
The fetus is far from being a passive passenger in its
mother’s womb. It kicks, turns, flexes its body, somersaults,
squints, and swallows, makes a fist, hiccups and sucks its
thumb. It responds to both sound and vibrations, showing
that it can hear and feel.
Stages of Prenatal Development
First month:
weeks to
distinct
and the
develop
Fertilization occurs
Zygote implants itself in the
lining of the uterus
Rapid cell division occurs
Embryonic stage lasts from 2
8 weeks
Cells differentiate into three
layers:
the ectoderm, the mesoderm,
endoderm
Nervous system begins to
Embryo is 1/2 inch long
6-Week-Old Embryo
(Rear View)
At 6 weeks, the embryo is just
over half an inch long. As shown
in this photograph, the arms
and legs are just beginning to
grow, and the head area is
extremely large compared to its
size after birth. The embryo is
shown here in the amniotic sac,
which is filled with fluid to
protect it.
Two Months
Heart and blood vessels form
Head area develops rapidly
Eyes begin to form detail
Internal organs grow, especially
the digestive system
Sex organs develop rapidly and
sex is distinguished
Arms and legs form and grow
Heart begins to beat faintly
Embryo is 1 inch long and weighs
1/10 ounce
Three Months
Head growth occurs rapidly
Bone formation begins to form
rapidly
The digestive organs begin to
function
Arms, legs, and fingers make
spontaneous movements
Fetus is 3 inches long and
weighs 1 ounce
4½-Month-Old Fetus
Sucking Thumb
At about 4½ months of
prenatal development,
the fetus is about 10
inches long and weighs
approximately 9 ounces.
As shown in this
photograph, the fetus
shows the reflexive
movement of sucking its
thumb. This activity
appears remarkably
similar to thumbsucking in neonates.
Six months
Eyes and eyelids fully formed
Fat is developing under the skin
Fetus is 14 inches long and
weighs 2 pounds
Nine months
Fetus settles into position for birth
The average baby is more than 19
inches long and weighs nearly 7
pounds now, but babies vary
widely in size at this stage
Miscarriage and Abortion
Causes
• chromosomal abnormalities
• viral or bacterial infections
• abnormalities of reproductive tract.
• severe trauma
Maternal Characteristics
Mother’s age
- Infants born to adolescents are often premature
and mortality rate of infants born to adolescents is
double than that of one born to mothers in their
20s.
- Babies with down’s syndrome are rarely born to
mothers below 30, but the risk is considered higher
for mothers below 18.
Nutrition
-Nutrition is very important too as children born to
malnourished mothers are likely to be malformed.
Emotional states
-Stress during pregnancy leads to physiological
changes and production of adrenaline
(usually in response to fear) which may restrict blood
flow to the uterine area and may deprive the fetus of
adequate oxygen.
-Maternal anxiety during pregnancy was also found
associated with infants who were more
hyperactive and irritable along with feeding and
sleeping problems.
Teratology and Hazards to prenatal Development
The field of study that investigates the causes of birth
defects is called teratology. Teratogen is any agent that
causes a birth defect.
The probability of structural defects is greatest early in
the embryonic period; during the fetal period they are
likely to stunt growth or create problems in the way
organs function.
For example, brain is most vulnerable at 15-25 days
after conception; eyes 24-40 days; heart at 24-40 days,
and legs at 24-36 days.
Maternal Diseases and Conditions
Rubella, syphilis and genital herpes are found to cause
death or deformities in children born to mothers who are
infected.
AIDS
• Mothers can infect their offsprings:
(1) during gestation across the placenta;
(2) during delivery through contact with blood or fluids;
(3) post-partum through breast-feeding.
• Approximately one-third born to infected mothers will
ultimately become infected.
• Babies can be infected and symptomatic; infected but
asymptomatic and not infected at all.
Drugs
• Tranquilizers like thalidomide, taken for morning
sickness are known to cause devastating effects on
fetus.
e.g. if a woman took on day 26, an arm might not grow.
• Fetal alcohol syndrome (FAS) is a cluster of
abnormalities that appear in the offspring of mothers
who drink heavily during pregnancy.
Fetal and neonatal deaths are higher among smoking
mothers; studies have also shown that exposure to
smoking was related to poor language and cognitive
development; mothers who smoked during pregnancy
had infants who were awake more on a consistent basis;
and respiratory problems and sudden infant death/ crib
death were found very common among the offsprings of
mothers who smoked during pregnancy.
Environmental Hazards
Radiation can cause gene mutation, an abrupt but
permanent change in genetic material. Even radiation
from X-rays can affect the fetus.
Birth
Stages of Birth:
.
Stage 1
uterine contractions are 15 - 20 mins apart and
(average of 12-24 hrs) lasts upto a min; contractions come closer as it
progresses increasing in intensity; and dilates the
cervix to an opening of 4“ for baby to move from
uterus to birth canal.
Stage 2
(lasts 1 and half hrs.)
head starts to move through the cervix and birth
canal.
Stage 3/ Afterbirth placenta, umbilical cord and other membrane
are detached and expelled.
Delivery Complications
• Precipitate delivery is a delivery that takes place too
rapidly - takes less than 10 minutes to be squeezed
through the birth canal. It can disturb infant’s normal
flow of blood and the pressure on infant’s head can cause
haemorrhaging.
• If delivery takes too long, anoxia or the insufficient
supply of oxygen to the infant can take place. Anoxia
can cause brain damage.
The breech position can cause respiratory problems and
some cannot pass through the cervix and has to be
delivered by a cesarean section
The Postpartum Period
It is a time when a woman’s body adjusts, both
physically and psychologically, having completed the
process of childbearing.
Physical adjustment:
Involution is the process by which the uterus returns to
its pre-pregnancy size 5 or 6 weeks after birth. Nursing
the baby helps to contract the uterus at a rapid rate.
Emotional and Psychological Adjustments:
Many women undergo a postpartum depression and can
have a considerable effect on the infant.