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Chapter 3:

Chapter 3:. Prenatal Development and Birth. In This Chapter. 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)

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Chapter 3:

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  1. Chapter 3: Prenatal Development and Birth

  2. In This Chapter

  3. Conception and GeneticsChromosomes, DNA, and Genes Process of conception • Ovum • Sperm • Zygote Chromosomes • DNA • Genes

  4. Conception and GeneticsSex Determination Chromosomes • Autosomes • Sex chromosomes (X, Y) Chromosomal differences • Androgens and SRY gene • Sex chromosomes (X, Y) • Gonad development

  5. Conception and GeneticsMultiple Births Twins Identical (monozygotic) Fraternal (dizygotic) Semi-identical (different genes from father)

  6. Stop and Think! Your textbook notes an increase in multiple births over the past thirty years. Why has this occurred?

  7. Conception and GeneticsHow Genes Influence Development Genotype: Genetic blueprint Phenotype: Observable characteristics Dominant–recessive pattern Polygenic inheritance

  8. 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?

  9. The Genetics of Hair Type

  10. Conception and GeneticsOther Types of Inheritance Genomic imprinting: Some genes biochemically marked at time ova and sperm develop Mitochondrial inheritance: Genes in mitochondria

  11. Conception and GeneticsMulti-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?

  12. Genetic DisordersAutosomal Disorders Autosomal gene: One of 22 pairs of autosomes that are involved in sex determination Autosomal recessive disorder: 2 copies of the abnormal gene must be present for the disease or trait to develop. Autosomal dominant disorder: abnormal gene from 1 parent sufficient to inherit disease or trait See Table 3.2 for a summary of some genetic disorders.

  13. Genetic DisordersSex-Linked Disorders Sex-linked disorders: Caused by recessive gene on X chromosome

  14. Stop and Think… Why do boys have Fragile X Syndrome more often than girls?

  15. Chromosomal ErrorsTrisomies and Monosomies Trisomies: Three chromosomes, rather than usual pair Monosomies: Absence of one member of chromosome pair

  16. Chromosomal ErrorsSex 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

  17. Pregnancy and Prenatal DevelopmentThe Mother’s Experience: First Trimester Care Regular prenatal care critical at this time Problems Ectopic pregnancy, bleeding, miscarriage

  18. Pregnancy and Prenatal DevelopmentThe Mother’s Experience: Second Trimester Care • Monthly doctor visits continue • Ultrasound Problems • Gestational diabetes; Rh incompatibility; increased blood pressure • Miscarriage; premature labor

  19. Pregnancy and Prenatal DevelopmentThe 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

  20. Pregnancy and Prenatal DevelopmentThe Prenatal Experience: Germinal Stage Conception to implantation Blastocyst implants Specialization of cells needed to support development

  21. Pregnancy and Prenatal DevelopmentThe 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.

  22. Pregnancy and Prenatal DevelopmentThe 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

  23. Figure 3.3: Parts of the Neuron Structure of a Single Neuron Cell bodies first to develop (wks 12-24) Axons and dendrites develop later (especially final 12 wks). Axons continue to increase in size and complexity after birth. Figure 3.3. Parts of the Neuron

  24. 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

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

  26. Prenatal BehaviorIntroducing 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.

  27. Figure 3.6 Correlations between Fetal Behavior and Brain Development

  28. ? ? Questions To Ponder You are told by a genetic counselor that you have 25 percent chance of passing on a deadly genetic trait to your child. Do you still have a child? What factors influence your choice? How do we curtail the use of teratogens, such as smoking and alcohol use, by pregnant women?

  29. Problems in Prenatal DevelopmentTeratogens See Figure 3.7 for timing of exposure First 8 weeks most dangerous exposure time Duration and intensity exposure important Teratogen: substance that can damage embryo Greatest damage during organ system’s most rapid development

  30. Figure 3.7 Timing of Teratogen Exposure

  31. Problems in Prenatal DevelopmentTeratogens: Drugs Prescription Over-the-counter drugs Marijuana, methamphetamine, and heroin Cocaine Tobacco Alcohol

  32. Problems in Prenatal DevelopmentTeratogens: Maternal Diseases Rubella (“German measles”) HIV Other sexually transmitted diseases

  33. Problems in Prenatal DevelopmentOther Maternal Influences: Diet Folic acid deficiencies Malnutrition • Neonate low birth weight • Brain stunting • Fetal death • Mental illness in adulthood

  34. Problems in Prenatal DevelopmentOther 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.

  35. Problems in Prenatal DevelopmentOther 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

  36. Problems in Prenatal DevelopmentEnvironmental Hazards Detrimental effects of hazards may be reduced by: Limiting exposure to lead and mercury Avoiding possible harmful chemicals

  37. Problems in Prenatal DevelopmentMaternal Emotions Maternal stress and depression related to higher risks for fetus Social support and counseling may help. Mixed information from research

  38. Fetal Assessment and Treatment

  39. Can you identify each method? Figure 3.8 Two Methods of Prenatal Diagnosis

  40. 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?

  41. Birth and the NeonateBirth Choices Things to consider Location of birth Birth attendants Drugs during labor and delivery “Natural childbirth”

  42. 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? http://www.childbirth.org/interactive/ibirthplan.html

  43. The Physical Process of BirthLabor: 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

  44. Figure 3.9 The Three Stages of Labor

  45. Figure 3.9 The Three Stages of Labor

  46. The Physical Process of BirthBirth Complications: Cesarean Deliveries • Why are Cesarean deliveries performed? • Fetal distress • Breech presentation • Birth size • Poor progress during labor • Mother’s health and age concerns

  47. The Physical Process of BirthAssessing the Neonate Apgar scale Brazelton Neonatal Behavioral Assessment Why is neonatal assessment important?

  48. Assessing the NeonateLow 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 risk of complications.

  49. Assessing the NeonateDo LBW babies catch up? Development best assessed on individual basis Two-thirds to three-fourths of preterm infants catch up by school entrance. Lowest birth weight and earlier gestational age associated with long-term developmental delays.

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