Pre-natal Development

1. What are some early signs of pregnancy?

2. 2 of 30
Stages of Prenatal Development
Zygotic (or Germinal) Stage 0-2 weeks
Embryonic Stage 2-8 weeks
Fetal Stage 9-40 weeks

3. Conception
Conception occurs when a sperm cell
penetrates and fertilizes an egg cell
Successful conception depends on
ovaries releasing one healthy egg cell
egg cell migrates most of the way down
the fallopian tube
One sperm must penetrate the ovum to
form a zygote.

4. Germinal Period
Begins when egg is fertilized in the
fallopian tube.
Period of rapid cell division
Ends 2 weeks later when the zygote is
implanted in the wall of the uterus

5. Germinal Period

6. Embryonic Period
From 2 to 8 weeks after conception
Cell differentiation intensifies
Life support systems for the
embryo develop
Organs Appear

7. Prenatal Structures

8. 8 of 30
At 2 weeks, the embryonic disk as 3 layers:
Entoderm: from which develops pharynx,
tonsils, thyroid, trachea, lungs, digestive
system, bladder, urethra
Mesoderm: from which develops muscles,
bones, circulatory system, lymph system,
kidneys, gonads
Ectoderm: from which develops skin, hair,
nails, sense organs, nervous tissue

9. Fetal Period
From 9 weeks after conception
to birth
Increase in size and systems
begin to function
Age of viability: 22 to 28 weeks

10. First Month
By the end of the
first month, the
embryo is about 1/10
of an inch long. The
heart, which is no
larger than a poppy
seed, has begun
beating.

11. First Month

12. Two Months
The embryo is about
1 inch long and has
distinct, slightly
webbed fingers.
Veins are clearly
visible. The heart
has divided into right
and left chambers.

13. Two Months

14. Three Months
By now the fetus is 2
1/2 to 3 inches long
and is fully formed. He
has begun swallowing
and kicking. All
organs and muscles
have formed and are
beginning to function.
Genitals can be now
identified as male or
female.

15. Four Months
Fetus is about 6
inches long and
weighs 4 to 7
ounces. His
heartbeat can be
heard clearly. This is
when you may feel
your baby's first
kick.

16. 4 months

17. Five Months
A protective coating
called vernix caseosa
begins to form on baby's
skin. By the end of this
month, your baby will be
nearly 12 inches long
and weigh almost a
pound. Fetus is more
active.

18. Six Months
Eyebrows and
eyelids are visible.
Your baby's lungs
are filled with
amniotic fluid, and
he has started
breathing motions. If
you talk or sing, he
can hear you.

19. 6 Months

20. Seven Months
By the end of the
seventh month, your
baby weighs about 3
1/2 pounds and is
about 12 inches
long. His body is
well-formed.
Fingernails cover
his fingertips

22. Eight Months
Your baby is gaining
about half a pound
per week, and
layers of fat are
piling on. He has
probably turned
head-down in
preparation for birth.
He weighs between
4 and 6 pounds.

24. Nine Months
Your baby is a hefty
6 to 9 pounds and
measures between
19 and 22 inches. As
he becomes more
crowded, you may
feel him move
around less.

25. Happy Birthday!!!

26. Factors Affecting to
Prenatal Development
General Risk Factors
Teratogens: Diseases, Drugs, and
Environmental Hazards
How Teratogens Influence Prenatal
Development
Prenatal Diagnosis and Treatment

27. General Risk Factors
Nutrition: adequate amount of food,
protein, vitamins, & minerals
Stress: decreases oxygen to fetus and
weakens mother’s immune system
Mother’s Age: neither too young, nor
too old

28. Prescription and Nonprescription Drugs –
Several drugs used by the mother that have
negative effects on the embryos and fetuses.
Psychoactive drugs are used to alter states of
consciousness, modify perceptions, and change
moods. The effects of alcohol, nicotine, and
illegal drugs on the fetus are well-documented.
Incompatibility of blood types where the
fetus’s blood is RH positive ad the mother’s is
RH negative cause antibodies to attack the
fetus, resulting in serious, often life-threatening
damage.

29. Environmental hazards of the modern world
can cause chromosomal abnormalities.
Exposure to toxins, radiation, pollutants, and
excess heat can all contribute to a negative
impact on the fetus.
Other maternal factors such as infectious
diseases (Rubella, Syphilis, AIDS), all have
varying degrees of impact on the fetus. Also
considered are emotional stress, age, and
nutrition of the mother.
Paternal factors can impact fetal growth
such as pesticides at the workplace, smoking
and diet.

30. Teratogens: Diseases, Drugs, and
Environmental Hazards
• Many diseases pass
through the placenta
directly and attack the
fetus
• Potentially dangerous
drugs not limited to
cocaine but include
alcohol and caffeine
• Environmental hazards
are treacherous because
we’re often unaware of
their presence

31. How Teratogens Influence Prenatal
Development
Not universally harmful
Harm particular structures at a
particular point in development in
particular animals

32. Effects of Teratogens

33. Prenatal Diagnosis and
Treatment
Diagnosis: ultrasound, amniocentesis,
and chorionic villus sampling can
detect physical deformities and genetic
disorders
Treatment: fetal medicine and genetic
engineering are experimental

34. Prenatal Diagnosis
Amniocentesis Chorionic Villus Sampling

35. Labor and Delivery
Stage 1: starts when the muscles of the
uterus contract and ends when the
cervix is fully enlarged (about 10 cm)
Stage 2: baby is pushed down the birth
canal
Stage 3: placenta is expelled

36. Three Stages of Labor