Transcript Chapter 5
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 The Period of Pregnancy and Prenatal Development • 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. The Period of Pregnancy and Prenatal Development • 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 The Period of Pregnancy and Prenatal Development • 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 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 human cell can be distinguished from one another. – In females, this pair is called XX, in males, it is called XY The Period of Pregnancy and Prenatal Development • 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 The Period of Pregnancy and Prenatal Development Figure 5.1 Diagram of a Small Part of a DNA Molecule The Period of Pregnancy and Prenatal Development • 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 The Period of Pregnancy and Prenatal Development • 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 The Period of Pregnancy and Prenatal Development Figure 5.3 Probability of Heterozygous Brown-Eyed Parents Producing Blue-Eyed Offspring The Period of Pregnancy and Prenatal Development • 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 The Period of Pregnancy and Prenatal Development The Period of Pregnancy and Prenatal 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 The Period of Pregnancy and Prenatal Development • 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 The Period of Pregnancy and Prenatal Development • 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 The Period of Pregnancy and Prenatal Development • 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 The Period of Pregnancy and Prenatal Development • 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 The Period of Pregnancy and Prenatal Development • Infertility and Alternative Means of Reproduction (cont.) – Many legal and ethical questions have arisen from these alternative means of reproduction The Period of Pregnancy and Prenatal Development Figure 5.7 Outcome of Assisted Reproductive Technology Cycles Using Fresh, Nondonor Eggs or Embryos,by Stage: 2001 The Period of Pregnancy and Prenatal Development • 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 The Period of Pregnancy and Prenatal Development • 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 The Period of Pregnancy and Prenatal Development • Development in the First Trimester: The Germinal and Embryonic Periods (cont.) – Examples of teratogens are viruses, medicines, alcohol, drugs, and environmental toxins 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 The Period of Pregnancy and Prenatal Development • 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 The Period of Pregnancy and Prenatal Development The Period of Pregnancy and Prenatal Development The Period of Pregnancy and Prenatal Development • 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 The Period of Pregnancy and Prenatal Development • 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 The Period of Pregnancy and Prenatal Development • 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 Period of Pregnancy and Prenatal Development • 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 The Period of Pregnancy and Prenatal Development • 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 The Period of Pregnancy and Prenatal Development • Impact of the Pregnant Woman on the Fetus (cont.) – Caffeine – Narcotics – Prescription Drugs – Obstetric Anesthetics – Environmental Toxins – Mother’s Diet The Period of Pregnancy and Prenatal Development Figure 5.9 Live Birthrates by Age of Mother, 1960-2000 The Period of Pregnancy and Prenatal Development • 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 Pregnancy and Prenatal Development • 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 The Period of Pregnancy and Prenatal Development • 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 The Period of Pregnancy and Prenatal Development • 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 The Period of Pregnancy and Prenatal Development The Period of Pregnancy and Prenatal Development • 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? 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 situation differently?