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The Prenatal Period
The Prenatal Environment: Threats
to Development
Fertilization
Moment of
conception
– Joining of sperm and
ovum = zygote
ANATOMY OF THE FEMALE
REPRODUCTIVE ORGANS
The basic anatomy of the
female reproductive organs is
illustrated in this cutaway view.
Source: Moore & Persaud, 2003.
Stages of Prenatal Development
Germinal
Embryonic
Fetal
Germinal Stage
Fertilization  two weeks
– Shortest stage
– Fertilized egg now called blastocyst
– Blastocyst travels to and implants in uterus
– Characterized by methodical cell division
– With division comes cell specialization
Embryonic Stage
2 weeks  8 weeks
– Organism firmly secures
to uterus and is called an
embryo
– Development of major
organs and basic
anatomy
Embyro at 5-6 weeks
Three distinct layers
that ultimately form
different sets of
structures:
– Ectoderm
– Endoderm
– Mesoderm
Body Proportions
During the fetal period,
the proportions of the
body change
dramatically.
At 2 months, the head
represents about half
the fetus, but by the
time of birth, it is onequarter of its total size.
Fetal Stage
8 weeks  Birth
Fetus at 8 weeks
Fetus at 14 weeks
– Formally starts when
differentiation of major
organs has occurred
– Organism now called
fetus
– Characterized by rapid
development
• Organs become more
differentiated and begin
working
• Interconnections
between body parts
become more complex
and integrated
• Brain becomes more
sophisticated
Pregnancy Problems
Pregnancy Problems
Infertility
• Parental age
• Use of illicit drugs, cigarettes, bouts of
STIs
Treatments
• Artificial insemination (ICI, IUI, IVF, GIFT,
ZIFT)
OLDER WOMEN AND RISKS OF PREGNANCY
Not only does the rate of infertility increase as women get older, but
the risk of chromosomal abnormality increases as well.
Source: Reproductive Medicine Associates of New Jersey, 2002.
Fertilization joins the sperm and ovum to start
prenatal development.
The prenatal period consists of three stages:
germinal, embryonic, and fetal.
In addition to difficulties in conceiving due
to infertility, some 15 to 20 percent of all
pregnancies end in miscarriage, usually in
the first several months of pregnancy.
The fertility treatment in which fertilization is
induced inside the mother's body is known
as_________.
a. artificial insemination
b. intracervical insemination
c. intrauterine insemination
d. in vitro fertilization
Fertilization that occurs outside the mother's
body is called ____________.
a. artificial insemination
b. infertility
c. in vitro fertilization (IVF)
d. intracervical insemination
In your opinion, is it wiser for a woman to ask
a friend or a stranger to be the surrogate
mother for her child?
Why?
The Prenatal Environment: Threats to
Development
Teratogen
• Includes environmental agent such as a drug,
chemical, virus, or other factor that produces a birth
defect
• Related to time and quantity of exposure
• (See Figure 2-12 or the next slide for a teratogen
sensitivity timeline)
Teratogen
Sensitivity
Timeline
Mother's Prenatal Influence
Diet
Age
Health
Drug Use
Alcohol Use
Tobacco Use
Father's Prenatal Influence
Tobacco use
Drug use
Alcohol use
Treatment of mother
Optimizing the Prenatal Environment
• Avoid X-rays and birth control pills; get rubella
vaccination
• Eat well and take prenatal vitamins
• Avoid alcohol use and other drugs
• Monitor caffeine intake.
• Avoid smoking and exposure to secondhand
smoke
• Exercise regularly
The prenatal environment significantly
influences the development of the baby. The
diet, age, prenatal support, and illnesses of
mothers can affect their babies' health and
growth.
Mothers' use of drugs, alcohol, tobacco, and
caffeine can adversely affect the health and
development of the unborn child. The
behavior of fathers and others also affect the
child.
Eating well and nutritiously, exercising
regularly, avoiding alcohol and tobacco, and
controlling caffeine intake are sound
strategies for averting threats to the fetal
environment.
Match the following descriptions of prenatal
development to their appropriate labels: germinal,
embryonic, and fetal.
a. This stage lasts from 8 weeks until birth and
involves the differentiation of major organs.
______________
b. From 2 to 8 weeks following fertilization, when the
major organs and basic anatomy begin developing.
______________
c. The first and shortest stage, where the zygote
begins to divide and grow in complexity during the first
2 weeks following conception. ______________
A ______________ is an environmental agent
such as a drug, chemical, virus, or other factor
that produces a birth defect.
a. terminal button
b. teratogen
c. terrapin
d. chromosome
Studies show that “crack babies” who are
now entering school have significant difficulty
dealing with multiple stimuli and forming close
attachments. How might both genetic and
environmental influences combined to
produce these results?