This document discusses prenatal development from conception through birth. It covers topics like the stages of prenatal development (germinal period, embryonic period, fetal period), what happens in each period like organ formation, common tests during pregnancy, risks from teratogens, and complications like low birth weight. The document emphasizes that the prenatal period involves the most dramatic transformation as the embryo and fetus develop all body parts and organ systems before birth.

2. 2
1. Introduction
2. Fact or Fiction?
3. Prenatal Development
4. Birth
5. Problems and Solutions
6. The New Family
7. Closing Thoughts

3. Introduction
3
Video:
The Prenatal Period: Conception to Birth

4. 4
Fact or Fiction? Fiction Fact
1. An embryo is the developing human
organism between the third and eighth
week after conception.
2. By the end of the third month, the
fetus has all of its body parts.
3. Teratogens are only a concern for
women who use alcohol and drugs.
4. All newborn reflexes
help a baby survive.

5. Beginning of
pregnancy
Pregnancy begins at conception, which is also the
starting point of gestational age. However, the
organism does not become an embryo until about
two weeks later, and pregnancy does not affect the
woman (and cannot be confirmed by blood or urine
testing) until implantation.
Length of
pregnancy
Full-term pregnancies last 266 days, or 38
weeks, or 9 months.
Trimesters
Instead of germinal period, embryonic period,
and fetal period, some writers divide pregnancy
into three-month periods called trimesters.
Due date
Although doctors assign a specific due date (based
on the woman’s LMP), only 5% of babies are born on
that exact date.
What is the timing and terminology of pregnancy?
Popular and professional books use various phrases to segment pregnancy.
The following comments may help to clarify the phrases used.
5
PRENATAL DEVELOPMENT

6. How does implantation occur?
The First 14 Days
implantation: The process beginning about 10
days after conception, in which the developing
organism nestles in, and attaches to the
placenta that lines the uterus.
The Most Dangerous Journey
Two-celled stage
Zygote
(single cell)
Fallopian
tube
Ovary
Ovum
Ova
Sperm
Implantation
Conception
6
PRENATAL DEVELOPMENT

7. What percentage of zygotes make it through each prenatal period?
The Germinal Period
The Embryonic Period
The Fetal Period
Birth
At least 60 percent of all developing organisms fail to grow or implant properly
and thus do not survive the germinal period. Most of these organisms are grossly
abnormal.
About 20 percent of all embryos are aborted spontaneously*, most often because
of chromosomal abnormalities.
About 5 percent of all fetuses are aborted spontaneously before viability at 22
weeks or are stillborn, defined as born dead after 22 weeks.
About 31 percent of all zygotes grow and survive to become living newborn
babies.
*Spontaneous abortions are also called miscarriages.
This table does not include induced abortions.
Sources: Bentley & Mascie-Taylor, 2000; K.L. Moore & Persaud, 2003.
Making it to Birth
7
PRENATAL DEVELOPMENT

8. Brain
Facial
Features
External
sex organs
Intestines
Arms, hands
and fingers
As nerves and muscles form links to the brain,
the embryo now moves spontaneously, as the
brain begins to move muscles.
Eyes and eyelids are developed. Eyes will continue
to migrate to the front of the head, where they
will eventually rest. Eyelids begin to grow
together and are only half closed. External,
middle, and inner ears are now fully formed.
External ears will continue to migrate to the side
of the head, where they will eventually rest.
Urogenital membranes have developed into either
male or female organs, and ovaries or testicles
are visible. Clitoris or penis begins to form, but
distinguishing the embryo’s sex is difficult.
The intestines begin to move from
the umbilical cord to the embryo’s
body cavity.
Arms are well formed, longer, and can
bend at elbows and move forward.
Fingers elongate and digits are fully
separated. Each finger has three digits,
and the thumb has two digits.
Overall
appearance
The head is still disproportionately large but is
erect and appears rounded. The neck is well
defined. The tail will disappear by the end of this
week. Cartilage begins to turn into bone. The
ectoderm layer is replaced by the beginnings of
skin. The body becomes evenly rounded, due to
the growth in the abdomen.
Brain
Facial
Features
External sex
organs Overall
appearance
Arms, hands
and fingersIntestines
8
What happens during the embryonic period of prenatal development?
From the Third through the Eighth Week
PRENATAL DEVELOPMENT

9. 9
From the Third Through the Eighth Week
Video:
The Prenatal Period: Brain Development
PRENATAL DEVELOPMENT

10. fetus: A developing human organism from the start of
the ninth week after conception until birth.
10
What happens during the fetal period of prenatal development?
9 12 16 20 24 28 32 36 38
From the Ninth Week until Birth
9 weeks through 38 weeks
PRENATAL DEVELOPMENT

11. Brain
stem
Hindbrain Neural tube
(forms spinal
cord)
Forebrain
(a) 25 days
Midbrain
Prenatal Growth of the Brain
How does the brain grow during the periods, or stages, of prenatal development?
11
Prenatal Brain Development
(b) 50 days (c) 100 days
(d) 20 weeks (e) 28 weeks
(f) 36 weeks (full term)
PRENATAL DEVELOPMENT

12. From the Ninth Week until Birth
12
Video:
The Prenatal Period: Conception to Birth
PRENATAL DEVELOPMENT

13. How do you feel about viewing the birth process?
1. A close friend or relative asks you to be present
during the labor and at the birth of her child.
You feel like saying:
Yes, I want to be there!
Yes, if you need me.
Maybe; let me think about it.
It’s something I don’t think I can do.
Don’t know; it’s hard to imagine.
2. You learn that someone took a photograph of the
moment of your birth. Are you:
Very eager to see the photograph?
Interested in seeing the photograph at some time?
Turned off by the thought of the photograph?
Both interested and turned off by the idea of the photograph?
Don’t know.
3. You learn that your class is scheduled to
see a film of a birth. Are you:
Very interested in seeing the film?
Somewhat interested in seeing the film?
Somewhat uneasy about seeing the film?
Very uneasy about seeing the film?
Both interested and uneasy?
13
RubberBall/SuperStock
BIRTH

14. 14
Video:
Birth
BIRTH

15. Apgar scale: A quick assessment of a newborn’s health, given twice
(at one minute and five minutes after birth).
How is a
Newborn tested?
15
First Minutes and Complications
BIRTH

16. What are the risks at different stages of development?
Birth Defects from Teratogens: Time of Exposure and Effect on Major Organs
Germinal Period Main Embryonic Period (in weeks) Fetal Period (in weeks)
Central nervous
system
Heart
Arms
Legs
Lips
Ears
Eyes
Teeth
Palate
Sex organs
Teratogens often
prevent implantation
Common site(s)
of action of
teratogens
Highly critical
period
Less critical
period
Neural-tube defects Mental retardation Learning disabilities
Cleft lip
Low-set malformed ears and deafness
Cataract, glaucoma
Enamel staining
Cleft palate
Masculinization of
female genitalia
Major congenital anomalies Functional defects and minor anomalies
1 2 3 4 5 6 7 8 9 16 32 38
Source: Adapted from K.L. Moore & Persaud. 2003 16
PROBLEMS AND SOLUTIONS

17. What are some prenatal tests?
17
Benefits of Prenatal Care
All photos: Stockbyte/Getty Images
PROBLEMS AND SOLUTIONS

18. Benefits of Prenatal Care
18
Video:
The Prenatal Period: Ultrasound
PROBLEMS AND SOLUTIONS

19. Low Birth Weight (LBW): A body weight at birth of less
than 5 ½ pounds (2,500 grams).
Very Low Birth Weight (VLBW): A body weight at birth
of less than 3 pounds, 5 ounces (1,500 grams).
Extremely Low Birth Weight (ELBW): A body weight at
birth of less than 2 pounds, 3 ounces; (1,000 grams).
Why is birth weight
important?
19
Variations in Birth Weight
Lagging physical and
cognitive development
confronts babies born
early (or preterm, once
called premature), and a
preterm baby also is
probably low birth
weight.
PROBLEMS AND SOLUTIONS

20. 20
Variations in Birth Weight
Video:
Low Birthweight in India
PROBLEMS AND SOLUTIONS

21. reflex: An unlearned, involuntary action or movement in
response to a stimulus.
What are some newborn reflex experiences?
21
Breathing reflexes Sucking reflexes Stepping reflexes Moro reflexes
THE NEW FAMILY

22. 22
Reflexes
Video:
Newborn Reflexes
THE NEW FAMILY

23. What is a father’s role?
23
Social Support
couvade: Symptoms of pregnancy and birth experienced by fathers.
Allphotos:Stockbyte/GettyImages
THE NEW FAMILY

24. 24
Social Support
Video:
The Experience of Pregnancy:
The First Trimester
THE NEW FAMILY

25. From what you discovered about prenatal development in these slides, what
examples can you cite to support the statement, “The most dramatic and
extensive transformation of the entire life span occurs before birth?”
Closing Thoughts
25
Allphotos:Stockbyte/GettyImages,exceptfor
lowermiddle,whichisRubberBall/SuperStock