chapter 5 - the period of pregnancy & prenatal development
TRANSCRIPT
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Chapter 5:
The Period of Pregnancy
and Prenatal Development
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The Period of Pregnancy and Prenatal Development
Chapter Objectives
To describe the biochemical basis of geneticinformation and the process through which
genetic information is transmitted from one
generation to the next
To identify the contributions of genetic factors
to individuality through their role in controlling
the rate of development, their contributions to
individual traits, and the genetic sources ofabnormalities
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Chapter Objectives (cont.)
To trace fetal development through threetrimesters of pregnancy, including an
understanding of critical periods when normal
fetal development can be disrupted
To describe the birth process and factors that
contribute to infant mortality.
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Chapter Objectives (cont.)
To analyze the reciprocity between thepregnant woman and the developing fetus,
focusing on ways in which pregnancy affects
a childbearing woman and expectant father
and on basic influences on fetal growth, suchas maternal age, drug use, nutrition, and
environmental toxins
To examine the impact of culture onpregnancy and childbirth
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Chapter Objectives (cont.)
To analyze abortion from a psychosocialperspective, including the legal context, its
social and emotional impact on women, and
mens views
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The Period of Pregnancy and Prenatal Development
Genes and Chromosomes as Sources of
Genetic Information Chromosomes are rodlike structures visible in
the nucleus, which store and transmit genetic
information.
There are 23 pairs of chromosomes residing
in each human cell, one is inherited from the
mother and one from the father.
The 23 pairs of chromosomes in each humancell can be distinguished from one another.
In females, this pair is called XX, in males, it is
called XY
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Genes and Chromosomes as Sources of
Genetic Information (cont.) The sex of the new organism is determined by
whether an X-bearing or a Y-bearing sperm
fertilizes the ovum
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Figure 5.1 Diagram of a Small Part of a DNA Molecule
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The Laws of Heredity
Basic principles of genetics were unknownuntil the mid-nineteenth century, when the
Austrian monk and botanist Gregor Mendel
began a series of experiments with pea plants
in his monastery garden
Alleles: each gene has at least 2 statesone
on each chromosome strand in the pair
Homozygous: both alleles are the same Heterozygous: alleles are different from each
other
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Genotype, Phenotype, and Influences of Alleles
Genotype: genetic information about a trait Phenotype: observed characteristic (e.g., eye
color, hair color)
Cumulative relation: when more than one pairof genes influence a trait (e.g., height)
Codominance: a pattern of inheritance in
which both alleles influence the persons
characteristics Dominance: when one alleles characteristics
are always observed
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Figure 5.3 Probability of Heterozygous Brown-Eyed Parents ProducingBlue-Eyed Offspring
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Sex-Linked Characteristics
Gene for specific characteristic is found onthe sex chromosome
Genetic Sources of Individual Differences Genetic determinants of the rate of
development
Genetic determinants of individual traits
Genetic determinants of abnormal
development
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Genetic Technology and Psychosocial Evolution
Today, genetic counseling and prenataldiagnosis permit people to make informed
decisions about conceiving or carrying a
pregnancy to term
Genetic counseling helps couples assess
their chances of giving birth to a baby with a
hereditary disorder
If couples who might bear an abnormal childdecide to conceive, several prenatal
diagnostic methods and medical procedures
that permit detection of problems before birth
are available
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Evaluating the Contribution of Genetic Factors to
Behavior Genetics and Intelligence
Specific genetic irregularities can cause degrees of
mental retardation
Understand the influence of genetics onintelligence through the study of family
relationships
The Reaction Range
A range of possible responses to environmental
conditions, the limits of which are determined by
ones genotype
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Twins
The zygote is the cell produced when thesperm and egg unite and fertilization occurs.
Monozygotic twins result when a zygote
divides in two and separates resulting in
identical twins
Dizygotic, or fraternal twins, result when
multiple ovulations and fertilizations occur
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Infertility and Alternative Means of Reproduction
Chances of experiencing infertility advancewith age
Infertility may place great stress on a
marriage
Artificial insemination is the injection of donor
sperm into the womans vagina to promote
conception
In Vitro fertilization is fertilization in an artificialenvironment or a Test tube baby. Fertilized
in a petri dish, a zygote is then implanted into
the mothers uterus
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Infertility and Alternative Means of Reproduction
(cont.) Gamete Intrafallopian Transfer (GIFT): Eggs
and sperm are transferred into a womans
fallopian tube and normal fertilization can then
occur
In Vivo Fertilization: fertilization in a living
body. A woman is artificially inseminated with
sperm, once fertilization occurs the zygote isthen transferred into the uterus of the mother
Surrogate mother: a woman conceives and
bears a child for an infertile couple
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Infertility and Alternative Means of Reproduction
(cont.) Many legal and ethical questions have arisen
from these alternative means of reproduction
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Figure 5.7 Outcome of Assisted Reproductive Technology CyclesUsing Fresh, Nondonor Eggs or Embryos,by Stage: 2001
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Development in the First Trimester: The
Germinal and Embryonic Periods The Period of the Zygote lasts about 2 weeks,
from fertilization until the tiny mass of cells
drifts down and out of the fallopian tube and
attaches itself to the wall of the uterus
The period of the embryo lasts from
implantation through the eighth week of
pregnancyAn amniotic sac forms that encloses the
developing organism in amniotic fluid. It
provides a cushion for the developing embryo
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Development in the First Trimester: The
Germinal and Embryonic Periods (cont.) The placenta is an organ that is newly form
with each pregnancy and expelled at birth.
Nutrients and waste pass through the
placenta from the mother to the developingchild
During these brief 6 weeks, the most rapid
prenatal changes take place as thegroundwork for all body structures and
internal organs is laid down. During this time
the embryo is sensitive to tetragons or agents
that can produce malformations in the fetus
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Development in the First Trimester: The
Germinal and Embryonic Periods (cont.) Examples of teratogens are viruses,
medicines, alcohol, drugs, and environmental
toxins
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The Period of Pregnancy and Prenatal Development
Development From the First to Third Trimester:
The Fetal Period Lasting from the ninth week until the end of
pregnancy, during this longest prenatal
period, the organism begins to increase
rapidly in size
In the third month, the organs, muscles, and
nervous system start to become organized
and connected. Between 17 and 20 weeks, the new being has
grown large enough that its movements can
be felt by the mother
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Development From the First to Third Trimester:
The Fetal PeriodAt the end of the second trimester, many
organs are quite well developed, and a major
milestone is reached in brain development, in
that all the neurons are now in place
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Caesarean Delivery
If natural childbirth is dangerous to the motheror the newborn, an alternative is to remove
the baby surgically through an incision in the
uterine wall. For example, in long labor,
breech position, and anoxia
Today there is debate if Caesarean sections
are too widely used by physicians
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Infant Mortality
The number of infants who die during the firstyear of life per 1,000 live births during that
year
In 2002, the U.S. rate was estimated at 7.0
deaths per 1,000 lived births up from 6.8 in
2001
Increases in multiple births, low birth weight
(under 2,500 grams), and premature births(less than 37 weeks) are all associated with
this increase
Two thirds of infant deaths occur during the
first month after birth
Th P i d f P d P l D l
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The Period of Pregnancy and Prenatal Development
Case Study: A Fathers Recollections
Thought Questions Given all the stress of the situation, what might
account for the very positive feelings reported by
Kunjufu at the moment of birth?
What are some different roles that men can playduring the childbirth process: What roles is Kunjufu
playing?
What might be some reasons that men do not want
to be present during labor and delivery? How do hospital personnel influence the
experiences of fathers during childbirth?
How might childbirth preparation classes influence
the experiences of fathers during childhood?
Th P i d f P d P l D l
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The Impact of the Fetus on The Pregnant
Woman Changes in roles and social status
Changes in the mothers emotional state
Fathers involvement during pregnancy and
childbirth
Th P i d f P d P t l D l t
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Impact of the Pregnant Woman on the Fetus
The Impact of Poverty Mothers Age
Maternal Drug Use
NicotineAlcohol
Fetal alcohol syndrome (FAS) refers to a disorder
in which mental retardation, poor attention, and
overactivity are typical of children with the disorder
Th P i d f P d P t l D l t
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Impact of the Pregnant Woman on the Fetus
(cont.) Caffeine
Narcotics
Prescription Drugs
Obstetric Anesthetics
Environmental Toxins
Mothers Diet
Th P i d f P d P t l D l t
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Figure 5.9 Live Birthrates by Age of Mother, 1960-2000
Th P i d f P d P t l D l t
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The Cultural Context
Reactions to Pregnancy Solicitude versus Shame - care, interest, and
help of others versus shame, condemnation,
and secrecy
Adequacy versus Vulnerability - sign of sexual
prowess and entrance into social status
versus tiring, exhaustion, and lots of work
The Period of Pregnanc and Prenatal De elopment
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Reactions to Childbirth
Every society marks the importance ofchildbirth in different ways
Americans focus on safety of the mother and
child, and toward building a sense of
competence in the mother and the father asthey approach the care of their newborn
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Applied Topic: Abortion
The decision to abort reflects the mothersattitude toward childbirth, her criteria for a
healthy normal child, her age and economic
resources, and her access to a safe means of
ending the pregnancy The decision also reflects the cultures
attitudes about the moral implication of ending
a life after conception and the legal principles
about when the fetus itself has a right to
societys protection
The decision to abort is related to its safety,
accessibility, and expense
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Applied Topic: Abortion (cont.)
The legal context of abortion in the UnitedStates
The incidence of legal abortions
The psychosocial impact of abortion
Mens reactions to abortion
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Case Study: Karen and Don
Thought Questions Try to put yourself in the roles of the main
characters in this case: Karen, Don, Karens
mother, Dons mother, and Dons father. How
might you react? How does technology enter this case?
How are the biological, psychological, and societal
systems involved in understanding the issues
faced by Karen and Don? How might Karen and Dons marital relationship be
influenced by these experiences?
What are the ethical considerations in this case?
The Period of Pregnancy and Prenatal Development
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The Period of Pregnancy and Prenatal Development
Case Study: Karen and Don (cont.)
Thought Questions (cont.) In what ways do cultural issues related to
pregnancy, childbirth, and abortion come into play
in this case? How might a couple living in a
different cultural context approach this situationdifferently?