Chapter 5: The Period of Pregnancy and Prenatal Development

Chapter 5:The Period of Pregnancy

and Prenatal Development

The Period of Pregnancy and Prenatal Development

• Chapter Objectives – To describe the biochemical basis of genetic

information 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 of abnormalities


• Chapter Objectives (cont.)– To trace fetal development through three

trimesters 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.


• Chapter Objectives (cont.)– To analyze the reciprocity between the

pregnant 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, such as maternal age, drug use, nutrition, and environmental toxins

– To examine the impact of culture on pregnancy and childbirth


• Chapter Objectives (cont.)– To analyze abortion from a psychosocial

perspective, including the legal context, its social and emotional impact on women, and men’s views


• 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 human cell can be distinguished from one another.

– In females, this pair is called XX, in males, it is called XY


• 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


Figure 5.1 Diagram of a Small Part of a DNA Molecule


• The Laws of Heredity– Basic principles of genetics were unknown

until 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 states—one on each chromosome strand in the pair

– Homozygous: both alleles are the same– Heterozygous: alleles are different from each

other


• 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 pair

of genes influence a trait (e.g., height)– Codominance: a pattern of inheritance in

which both alleles influence the person’s characteristics

– Dominance: when one alleles’ characteristics are always observed


Figure 5.3 Probability of Heterozygous Brown-Eyed Parents Producing Blue-Eyed Offspring


• Sex‑Linked Characteristics– Gene for specific characteristic is found on

the sex chromosome

• Genetic Sources of Individual Differences– Genetic determinants of the rate of

development– Genetic determinants of individual traits– Genetic determinants of abnormal

development



• Genetic Technology and Psychosocial Evolution– Today, genetic counseling and prenatal

diagnosis 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 child decide to conceive, several prenatal diagnostic methods and medical procedures that permit detection of problems before birth are available


• 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 on intelligence through the study of family relationships

– The Reaction Range• A range of possible responses to environmental

conditions, the limits of which are determined by one’s genotype


• Twins– The zygote is the cell produced when the

sperm 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


• Infertility and Alternative Means of Reproduction– Chances of experiencing infertility advance

with age– Infertility may place great stress on a

marriage– Artificial insemination is the injection of donor

sperm into the woman’s vagina to promote conception

– In Vitro fertilization is fertilization in an artificial environment or a ‘Test tube baby’. Fertilized in a petri dish, a zygote is then implanted into the mother’s uterus


• Infertility and Alternative Means of Reproduction (cont.)– Gamete Intrafallopian Transfer (GIFT): Eggs

and sperm are transferred into a woman’s 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 is then transferred into the uterus of the ‘mother’

– Surrogate mother: a woman conceives and bears a child for an infertile couple


• Infertility and Alternative Means of Reproduction (cont.)– Many legal and ethical questions have arisen

from these alternative means of reproduction


Figure 5.7 Outcome of Assisted Reproductive Technology Cycles Using Fresh, Nondonor Eggs or Embryos,by Stage: 2001


• 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 pregnancy

– An amniotic sac forms that encloses the developing organism in amniotic fluid. It provides a cushion for the developing embryo


• 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 developing child

– During these brief 6 weeks, the most rapid prenatal changes take place as the groundwork 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


• Development in the First Trimester: The Germinal and Embryonic Periods (cont.)– Examples of teratogens are viruses,

medicines, alcohol, drugs, and environmental toxins


• 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


• Development From the First to Third Trimester: The Fetal Period– At 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




• Caesarean Delivery– If natural childbirth is dangerous to the mother

or 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


• Infant Mortality– The number of infants who die during the first

year 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


• Case Study: A Father’s 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 play during 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?


• The Impact of the Fetus on The Pregnant Woman– Changes in roles and social status– Changes in the mother’s emotional state– Fathers’ involvement during pregnancy and

childbirth


• Impact of the Pregnant Woman on the Fetus– The Impact of Poverty– Mother’s Age– Maternal Drug Use– Nicotine– Alcohol

• Fetal alcohol syndrome (FAS) refers to a disorder in which mental retardation, poor attention, and overactivity are typical of children with the disorder


• Impact of the Pregnant Woman on the Fetus (cont.)– Caffeine– Narcotics– Prescription Drugs– Obstetric Anesthetics– Environmental Toxins– Mother’s Diet


Figure 5.9 Live Birthrates by Age of Mother, 1960-2000


• 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


• Reactions to Childbirth– Every society marks the importance of

childbirth 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 as they approach the care of their newborn


• Applied Topic: Abortion– The decision to abort reflects the mother’s

attitude 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 culture’s attitudes about the moral implication of ending a life after conception and the legal principles about when the fetus itself has a right to society’s protection

– The decision to abort is related to its safety, accessibility, and expense


• Applied Topic: Abortion (cont.)– The legal context of abortion in the United

States– The incidence of legal abortions– The psychosocial impact of abortion

• Men’s reactions to abortion



• Case Study: Karen and Don– Thought Questions

• Try to put yourself in the roles of the main characters in this case: Karen, Don, Karen’s mother, Don’s mother, and Don’s 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 Don’s marital relationship be influenced by these experiences?

• What are the ethical considerations in this case?


• 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 situation differently?

Documents

Chapter 5: The Period of Pregnancy and Prenatal Development