Prenatal Development and Birth Chapter 3:

IN THIS CHAPTER

LEARNING OBJECTIVES 3.1 What are the characteristics of the zygote? 3.2 In what ways do genes influence development? 3.3 What are the effects of the major dominant, recessive, and sex-linked diseases? 3.4 How do trisomes and other disorders of the autosomes and sex chromosomes affect development? 3.5 What are the characteristics of each trimester of pregnancy? 3.6 What happens in each stage of prenatal development? 3.7 How do male and female fetuses differ? 3.8 What behaviors have scientists observed in fetuses? 3.9 How do teratogens affect prenatal development?

LEARNING OBJECTIVES (con’t) 3.10 What are the potential adverse effects of tobacco, alcohol, and other drugs on prenatal development? 3.11 What risks are associated with teratogenic maternal diseases? 3.12 What other maternal factors influence prenatal development? 3.13 How do physicians assess and manage fetal health? 3.14 What kinds of birth choices are available to expectant parents? 3.15 What happens in each of the three stages of labor? 3.16 What do physicians learn about a newborn from the Apgar and Brazelton scales? 3.17 Which infants are categorized as low birth weight, and what risks are associated with this status?

CONCEPTION AND GENETICS Chromosomes, DNA, and Genes Process of Conception  Ovum  Sperm  Zygote Chromosomes  DNA  Genes

CONCEPTION AND GENETICS Sex Determination Chromosomes  Autosomes  Sex chromosomes (X, Y) Chromosomal Differences  Androgens and SRY gene  Sex chromosomes (X, Y)  Gonad development

CONCEPTION AND GENETICS Multiple Births Twins Identical (monozygotic) Fraternal (dizygotic) Semi-identical (different genes from father)

STOP AND THINK! Your textbook notes an increase in multiple births over the past thirty years. Why has this occurred?

CONCEPTION AND GENETICS How Genes Influence Development Genotype: genetic blueprint Phenotype: observable characteristics Dominant–recessive pattern Polygenic inheritance

Twins in Genetic Research Comparison of identical and fraternal twins has been been used for many decades to exam the role of heredity in human development. Identical twins are more similar than fraternal twins on measures of emotionality, activity, sociability, and intelligence Yet correlations that twins researchers have found are less than +1.00, even for identical twins who grow up in the same home. This offers strong evidence that psychological traits are clearly influenced by heredity. This might not be true for physical traits. Can you apply this information?

Critical Analysis 1. Fraternal twins are no more genetically similar than non-twin siblings, yet the IQs of fraternal twins are more strongly correlated than those of non-twin brothers and sisters. What explanations can you think of to explain this difference? 2. The term environment is extremely broad. What are some of the individual variables that comprise an individual’s environment?

LET’S TAKE A LOOK… Whose hair do you have? On the next slide you will see the genetics of hair type. Did you answer the above question correctly?

THE GENETICS OF HAIR TYPE

GENETIC SOURCES OF NORMAL TRAITS

CONCEPTION AND GENETICS Other Types of Inheritance Genomic imprinting: some genes biochemically marked at time ova and sperm develop Mitochondrial inheritance: genes in mitochondria

CONCEPTION AND GENETICS Multi-Factorial Inheritance (MFI) MFI: inheritance affected by genes and environment Five general principles (Rutter et al.) In what ways have genetics and environment integrated to influence your development?

GENETIC DISORDERS Autosomal Disorders Autosomal gene: one of twenty-two pairs of autosomes that are involved in sex determination Autosomal recessive disorder: two copies of the abnormal gene must be present for the disease or trait to develop. Autosomal dominant disorder: abnormal gene from one parent sufficient to inherit disease or trait See Table 3.2 (p. 55) for a summary of some genetic disorders.

SOME GENETIC DISORDERS

SEX-LINKED INHERITANCE

GENETIC DISORDERS Sex-Linked Disorders Sex-linked disorders: caused by recessive gene on X chromosome Red–Green ColorblindnessHemophiliaFragile X Syndrome

STOP AND THINK… Why do boys have Fragile X Syndrome more often than girls do?

CHROMOSOMAL ERRORS Trisomies and Monosomies Trisomies: three chromosomes, rather than the usual pair Monosomies: absence of one member of chromosome pair

CHROMOSOMAL ERRORS Sex Chromosome Anomalies Trisomy 21: Down syndrome XXY: Klinefelter’s syndrome XO: Turner’s syndrome XXX: girls with an extra X XYY: boys with an extra Y

PREGNANCY AND PRENATAL DEVELOPMENT The Mother’s Experience: First Trimester Care Regular prenatal care critical at this time Problems Ectopic pregnancy, bleeding, miscarriage

PREGNANCY AND PRENATAL DEVELOPMENT The Mother’s Experience: Second Trimester Care  Monthly doctor visits continue  Ultrasound Problems  Gestational diabetes; Rh incompatibility; increased blood pressure  Miscarriage; premature labor

PREGNANCY AND PRENATAL DEVELOPMENT The Mother’s Experience: Third Trimester Care Weekly visits (beginning in 32nd week) Ultrasound to assess position; pelvic exam to check cervical dilation Problems  Increased blood pressure, bleeding, bladder infection  Premature labor

PREGNANCY AND PRENATAL DEVELOPMENT The Prenatal Experience: Germinal Stage Conception to Implantation Blastocyst implants Specialization of cells needed to support development

PREGNANCY AND PRENATAL DEVELOPMENT The Prenatal Experience: Embryonic Stage 2 to 8 Weeks after Conception Neural tube develops. Forms foundations of all body organs and systems Many organs and systems begin to function.

PREGNANCY AND PRENATAL DEVELOPMENT The Prenatal Experience: Fetal Stage End of Week 8 until Birth Growth from 1/4 ounce and 1 inch to 7 pounds and 20 inches in length Refinement of all organ systems Neuronal proliferation Viable at Week 24; full-term at Week 37

PARTS OF THE NEURON Structure of a Single Neuron Cell bodies first to develop (weeks 12–24). Axons and dendrites develop later (especially final 12 weeks). Axons continue to increase in size and complexity after birth. Figure 3.3. Parts of the Neuron

FETAL DEVELOPMENT Figure 3.4 Fetal yawning appears between the 10th and 15th week. Its presence signals the beginning of sleep stages in the fetal brain. Figure 3.5 Glial cells that develop during the last few months of prenatal development hold neurons together and give form and structure to the fetal brain. (Source: Brown, Estroff, & Barnenott, 2004.)

PRENATAL SEX DIFFERENCES Males  More physically active  Higher rates of miscarriage  More vulnerable to prenatal problems Females  More sensitive to external stimulation  More rapid skeletal development

PRENATAL SEX DIFFERENCES Some researchers suggest : Males More physically active More vulnerable to prenatal problems Females More sensitive to external stimulation More rapid skeletal development Other researchers contend: Sex differences in: Prenatal hormones linked to cross-gender variations Prenatal problems Can you guess what these might be?

PRENATAL BEHAVIOR Introducing the Amazing Fetus! Fetuses can differentiate between familiar and novel stimuli by 32 to 33 weeks. Newborns can remember prenatal stimuli and react accordingly. Very active fetuses tend to be active children who can be labeled “hyperactive” later on.

Teratogen: substance that can damage embryo See Figure 3.7 for timing of exposure Greatest damage during organ system’s most rapid development First 8 weeks most dangerous exposure time Duration and intensity exposure i mportant PROBLEMS IN PRENATAL DEVELOPMENT TERATOGENS

THE TIMING OF TERATOGEN EXPOSURE

PROBLEMS IN PRENATAL DEVELOPMENT Teratogens: Maternal Diseases Cancer Toxoplasmosis Chicken pox Parvovirus Hepatitis B Chlamydia Tuberculosis

PROBLEMS IN PRENATAL DEVELOPMENT Teratogens: Drugs Inhalants Accutane/vitamin A Streptomycin Penicillin Tetracycline Diet pills

PROBLEMS IN PRENATAL DEVELOPMENT Teratogens: Drugs Prescription Over-the-counter drugs Marijuana, methamphetamine, and heroin Cocaine Tobacco Alcohol

PROBLEMS IN PRENATAL DEVELOPMENT Other Maternal Influences: Diet Folic acid deficiencies Malnutrition  Neonate low birth weight  Brain stunting  Fetal death  Mental illness in adulthood

PROBLEMS IN PRENATAL DEVELOPMENT Other Maternal Influences: Age First pregnancies are occurring later—average age is now 25.1 years. Women over 35 have higher risks for pregnancy complications. Teenage mothers have higher risks during and after birth.

PROBLEMS IN PRENATAL DEVELOPMENT Other Maternal Influences: Chronic Illnesses Kinds of Illness Depression Epilepsy Diabetes Lupus Prevention Monitoring of mother and fetus necessary for most illnesses Fetal–maternal specialist for high-risk patient

PROBLEMS IN PRENATAL DEVELOPMENT Environmental Hazards Detrimental effects of hazards may be reduced by: Limiting exposure to lead and mercury Avoiding possible harmful chemicals

PROBLEMS IN PRENATAL DEVELOPMENT Maternal Emotions Maternal stress and depression are related to higher risks for the fetus. Social support and counseling may help. Mixed information from research

FETAL ASSESSMENT AND TREATMENT UltrasonographyChorionic Villus Sampling (CVS)AmniocentesisAlpha-Fetoprotein Blood TestFetoscopy

CAN YOU IDENTIFY EACH METHOD?

STOP AND THINK! With the advent of antiretroviral drugs, the rate of mother-to-fetus transmission has been greatly reduced. Do these findings justify mandatory testing and treatment of pregnant women who are at high risk of having HIV/AIDS?

BIRTH AND THE NEONATE Birth Choices Things to Consider Location of birth Birth attendants Drugs during labor and delivery “Natural childbirth”

WANT TO MAKE A BIRTH PLAN? How would you plan the ideal birth for yourself, a partner, or a friend? Go to the link below to develop your birth plan. Did you include everything in your above ideal plan?

THE PHYSICAL PROCESS OF BIRTH Labor: An Overview Stage 1  Contractions  Dilation of the cervix Stage 2  Actual delivery of the baby Stage 3  Delivery of the placenta and umbilical cord

THE THREE STAGES OF LABOR

THE PHYSICAL PROCESS OF BIRTH Birth Complications: Cesarean Deliveries Why are Cesarean deliveries performed? Fetal distress Breech presentation Birth size Poor progress during labor Mother’s health and age concerns

THE PHYSICAL PROCESS OF BIRTH Assessing the Neonate Apgar scale Brazelton Neonatal Behavioral Assessment Why is neonatal assessment important?

THE APGAR SCALE

ASSESSING THE NEONATE Low-Birth-Weight Babies (LBW) LBW: below 2,500 grams (5.5 pounds) Preterm: mostly born before Week 38 Small-for-date neonates Risks Respiratory distress syndrome Intervention Adequate parental education and support reduces the risk of complications.

ASSESSING THE NEONATE Do LBW babies catch up? Development is best assessed on an individual basis. Two-thirds to three-fourths of preterm infants catch up by school entrance. Lowest birth weight and earlier gestational age are associated with long-term developmental delays.

SINGING TO PRETERM INFANTS The use of music by NICU staff and parents to support the development of preterm infants is an active area of research in the emerging field of music therapy. Ate more and gained weight faster Discharged earlier Higher oxygen saturation levels Stronger infant–parent emotional bond

Reflection 1.How could the research on singing to preemies be put into practice in neonatal intensive care units in nondisruptive ways? 2.If you were responsible for helping parents of newborns understand the value of singing to their babies, how would you explain the relevant research to them?

WHEN DO PRETERM INFANTS CATCH UP WITH FULL-TERM INFANTS? Although many premature infants catch up with their peers by the time they go to school, developmentalists caution that the development of preterm children is best assessed on a case-by-case basis. Several factors influence development. Birth weight Gestational weight Parental responses

You Decide Decide which of these two statements you most agree with and think about how you would defend your position: 1.Two-thirds to three-quarters of premature infants catch up to their peers by the time they go to school, so it’s best to adopt a “wait and see” attitude toward your child’s development before attempting to influence it in order to avoid pushing the child beyond his or her limits.

You Decide 2.Both parental responses and realistic expectations are important in parenting a child who was born prematurely, so it’s best to do everything possible to enhance your child’s development without expecting him or her to develop in exactly the same way as a child who was born at term.