2. Introducing the topic
Prenatal development is the process in which
an embryo and later fetus develops during
gestation. Prenatal development starts with
fertilization the first stage in embryogenesis
which continues in fetal development until
birth.
3. In human pregnancy, prenatal
development, also known as antenatal
development, is the development of the
embryo following fertilization, and
continued as fetal development. By the end
of the tenth week of gestational age the
embryo has acquired its basic form and is
referred to as a fetus. The next period is
that of fetal development where many
organs become fully developed. This fetal
period is described both topically (by
organ) and chronologically (by time) with
major occurrences being listed by
gestational age.
5. Fertilization embryonic period: During each normal menstrual cycle one egg (ovum) is usually released from one of the ovaries, about 14
days after the last menstrual period. Release of the egg is called ovulation. The egg is swept into the funnel-shaped end of one of the fallopian
tubes.
Fetal development: The growth and maturation of the fetus in utero. This is divided into three periods: the preembryonic period begins with
conception and ends on gestational day 14; the embryonic period encompasses gestational weeks 3 through 8; and the remainder of the pregnancy
is known as the fetal period. Body organs and systems arise from three primary germ layers (ectoderm, mesoderm, and endoderm) and rudimentary
formation of all organ systems is completed by gestational week 16. Systems maturation essential to extrauterine survival begins during week 24
with the formation of pulmonary surfactant. Two critical events occur between weeks 26 and 29: the pulmonary vasculature becomes capable of gas
exchange and the central nervous system becomes capable of controlling respiration.
Congenital abnormalities: Congenital anomalies are also known as birth defects, congenital disorders or congenital malformations.
Congenital anomalies can be defined as structural or functional anomalies (for example, metabolic disorders) that occur during intrauterine life and
can be identified prenatally, at birth, or sometimes may only be detected later in infancy, such as hearing defects.
Prematurity: A premature birth is a birth that takes place more than three weeks before the baby is due. In other words, a premature birth is one
that occurs before the start of the 37th week of pregnancy. Normally, a pregnancy usually lasts about 40 weeks.
6. The steps of the development
Month 1-2
Month 1: As the fertilized egg grows, a water-tight sac
forms around it, gradually filling with fluid. This is called the
amniotic sac, and it helps cushion the growing embryo.The
placenta also develops. The placenta is a round, flat organ that
transfers nutrients from the mother to the baby, and transfers
wastes from the baby.
Month 2: Your baby's facial features continue to develop.
Each ear begins as a little fold of skin at the side of the head.
Tiny buds that eventually grow into arms and legs are forming.
Fingers, toes and eyes are also forming.The neural tube (brain,
spinal cord and other neural tissue of the central nervous
system) is well formed. The digestive tract and sensory organs
begin to develop. Bone starts to replace cartilage.
7. Month 3-4
Month 3: Your baby's arms, hands, fingers,
feet, and toes are fully formed. Your baby can
open and close its fists and mouth. Fingernails
and toenails are beginning to develop and the
external ears are formed. The beginnings of teeth
are forming. Your baby's reproductive organs
also develop, but the baby's gender is difficult to
distinguish on ultrasound.By the end of the third
month, your baby is fully formed.
Month 4: Your baby's heartbeat may now be
audible through an instrument called a doppler.
The fingers and toes are well-defined. Eyelids,
eyebrows, eyelashes, nails, and hair are formed.
Teeth and bones become denser. Your baby can
even suck his or her thumb, yawn, stretch, and
make faces.The nervous system is starting to
function.
8. Month 5-6
Month 5: You may begin to feel your baby
move, since he or she is developing muscles
and exercising them. This first movement is
called quickening.Hair begins to grow on
baby's head. Your baby's shoulders, back, and
temples are covered by a soft fine hair called
lanugo. This hair protects your baby and is
usually shed at the end of the baby's first
week of life.
Month 6: Your baby's skin is reddish in
color, wrinkled, and veins are visible through
the baby's translucent skin. Baby's finger and
toe prints are visible. The eyelids begin to part
and the eyes open.Baby responds to sounds .
9. Month 7-8
Month 7: Your baby will continue to
mature and develop reserves of body fat.
Your baby's hearing is fully developed. He or
she changes position frequently and
responds to stimuli, including sound, pain,
and light. The amniotic fluid begins to
diminish.
Month 8: Your baby will continue to
mature and develop reserves of body fat. You
may notice that your baby is kicking more.
Baby's brain is developing rapidly at this time,
and your baby can see and hear. Most
internal systems are well developed, but the
lungs may still be immature.Your baby is
about 18 inches long and weighs as much as
5 pounds.
10. Month 9
Month 9: Your baby continues to
grow and mature: the lungs are
nearly fully developed.Your baby's
reflexes are coordinated so he or
she can blink, close the eyes, turn
the head, grasp firmly, and respond
to sounds, light, and touch. Baby is
definitely ready to enter the
world!You may notice that your
baby moves less due to tight space.
Your baby's position changes to
prepare itself for labor and delivery.
The baby drops down in your pelvis.
Usually, the baby's head is down
toward the birth canal.Your baby is
about 18 to 20 inches long and
weighs about 7 pounds.
11. Chromosomes and Genetics
Overview
Chromosomes are structures within cells that
contain a person's genes ;
A gene is a segment of DNA and contains the
code for a specific protein that functions in one
or more types of cells in the body ;
Every normal human cell, except for sperm and
egg cells, has 23 pairs of chromosomes for a
total of 46 chromosomes. ;
Sperm and egg cells have only one of each pair
of chromosomes for a total of 23 ;
Normal people have 2 sex chromosomes, and
each is either an X or a Y chromosome ;
Normal females have two X chromosomes (XX),
and normal males have one X and one Y
chromosome (XY).
12. Genetic Abnormalities
Small changes (mutations) may occur
in a specific gene ;
Some substances or agents in the
environment are capable of damaging
and causing mutations in genes, and
these mutations may be passed from
parent to child. These substances are
called mutagens.
13. Chromosomal Abnormalities
Chromosomal abnormalities can
affect any chromosome, including
the sex chromosomes ;
Chromosomal abnormalities affect
the number or structure of
chromosomes and may be visible
with a microscope in a test called
karyotype analysis ;
Numerical abnormalities occur when
a person has one or more extra
copies of a chromosome (one extra
is trisomy, and two extra is
tetrasomy) or is missing a
chromosome (monosomy) ;
14. Testing for chromosomal and genetic
abnormalities
A person's chromosomes and
genes can be evaluated by
analyzing a sample of blood ;
Amniocentesis –is a diagnostic
procedure in which a needle is
inserted into the womb of a
pregnant woman and a small
amount of amniotic fluid is
removed ;
Chorionic villus sampling-
procedure that analyzes samples of
placental tissue to assess fetal
wellbeing.
15. Missing a part of a chromosome
A number of syndromes can occur
in infants who are missing parts of
chromosomes ;
These syndromes are called
chromosome deletion syndromes :
o cri du chat syndrome (cat’s cry
syndrome) ;
o Prader-Willi syndrome ;
o Wolf-Hirschhorn syndrome ;
