Presentation on theme: "Prenatal Development and Birth"— Presentation transcript:
1 Prenatal Development and Birth Chapter 3:Prenatal Development and Birth
2 In This Chapter Conception and genetics Genetic and chromosomal disordersPregnancy and prenatal developmentProblems in prenatal developmentBirth and the neonate
3 Conception and Genetics Chromosomes, DNA, and Genes Process of conceptionOvumSpermZygoteChromosomesDNAGenesConception and GeneticsThe first step in the development of an individual human being happens at conception when a sperm fertilizes an ovum (egg cell). The sperm moves from the vagina through the cervix and the uterus, finally meeting the ovum in the fallopian tube.The process of meiosis can be explained to help students understand that both ovum and sperm have 23 single (unpaired) chromosomes. You may want to mention that there are approximately 30,000 genes on the 23 chromosome pairs.At conception, the combination of genes from the father in the sperm and the mother in the ovum creates a unique genetic blueprint—the genotype—that characterizes the individual. The phenotype is comprised of an individual’s actual characteristics. The simplest set of genetic rules is the dominant–recessive pattern in which a single dominant gene strongly influences phenotype.
4 Conception and Genetics Sex Determination ChromosomesAutosomesSex chromosomes (X, Y)Chromosomal differencesAndrogens and SRY geneGonad developmentCongenital adrenal hyperplasia
5 Conception and Genetics Multiple Births TwinsIdentical (monozygotic)Fraternal (dizygotic)Semi-identical (different genes from father)Conception and GeneticsFraternal twins come from two eggs that are fertilized by two separate sperm; identical twins result when a single fertilized ovum separates into two parts and each develops into a separate individual. Assisted reproductive techniques are available to couples who have trouble conceiving.At conception, the combination of genes from the father in the sperm and the mother in the ovum creates a unique genetic blueprint—the genotype—that characterizes the individual. The phenotype is comprised of an individual’s actual characteristics. The simplest set of genetic rules is the dominant–recessive pattern in which a single dominant gene strongly influences phenotype.
6 Stop and Think!Your textbook notes an increase in multiple births over the past thirty years. Why has this occurred?
7 Conception and Genetics How Genes Influence Development Genotype: Genetic blueprintPhenotype: Observable characteristicsDominant–recessive patternPolygenic inheritanceAt conception, the combination of genes from the father in the sperm and the mother in the ovum creates a unique genetic blueprint—the genotype—that characterizes the individual. The phenotype is comprised of an individual’s actual characteristics. The simplest set of genetic rules is the dominant–recessive pattern in which a single dominant gene strongly influences phenotype.Dominant–recessive patternDominant genes always express their characteristics.Recessive genes come in pairs to express their characteristics.Polygenic InheritanceMany genes blend together to increase genetic outcomes seen in the phenotype
8 Whose hair do you have? Let’s Take a Look… On the next slide you will see the genetics of hair type. Did you answer the above question correctly?Ask students to use Figure 3.1 to map out how they got their hair type.CAUTION: Be sensitive to students who do not have access to information about their biological parent(s).
9 The Genetics of Hair Type As a follow-up: Go to Table 3.1 to discuss genetic sources of normal traits.
10 Conception and Genetics Other Types of Inheritance Genomic imprinting: Some genes biochemically marked at time ova and sperm developMitochondrial inheritance: Genes in mitochondriaPolygenic: many genes influence the phenotype.Skin color: 3 genes that may blend dark and light colored genesEye color: variations that offer multiple color possibilitiesHeight: multiple genes work together to determine a child’s height.Genomic imprinting: a defective gene will have one effect if inherited from the mother and a different effect if the gene is inherited from the father: chromosome 15 causes Prader-Willi Syndrome when inherited from the mother, and causes Angelman Syndrome when inherited from the father.Mitochondrial Inheritance: genes in mitochondria, fluid surrounding nucleus of ovum before fertilzation
11 Conception and Genetics Multi-Factorial Inheritance (MFI) MFI: Inheritance affected by genes and environmentFive general principles (Rutter et al.)In what ways have genetics and environment integrated to influence your development?Rutter principlesIndividual differences in reactivity to environmentTwo-way interplay between people and environmentPeople-environment interplay considered in ecological frameworkPeople process experiences rather than just serving as passive recepients of environmental forces.People act on their environment to shape and select their experiences.
12 Genetic Disorders Autosomal 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.Disorders caused by recessive genes:Phenylketonuria (PKU)Sickle-cell diseaseTay-Sachs diseaseDisorders caused by dominant genes:Huntington’s diseaseAutosomal disorders:PKU: common; caused by lack of the ability to metabolize a protein, phenylalanineSickle-cell anemia: defect creates sickle-shaped red blood cells; offers protection against malariaTay-Sachs causes death by age three.Huntington’s disease is a deterioration of the ventricles of the brain.
13 Genetic Disorders Sex-Linked Disorders Sex-linked disorders: Caused by recessive gene on X chromosomeRed–Green ColorblindnessHemophiliaFragile X SyndromeBoys suffer more often than girls.
14 Stop and Think…Why do boys have Fragile X Syndrome more often than girls?
15 Chromosomal Errors Trisomies and Monosomies Trisomies: Three chromosomes, rather than usual pair Monosomies: Absence of one member of chromosome pairTrisomy 21: Down syndromeMental retardationDistinctive facial featuresPhysical abnormalitiesMaternal age is a major factor.
16 Chromosomal Errors Sex Chromosome Anomalies Trisomy 21: Down syndromeXXY: Klinefelter’s syndromeXO: Turner’s syndromeXXX: girls with an extra XXYY: boys with an extra YTrisomy 21: Down syndromeMental retardationDistinctive facial featuresPhysical abnormalitiesMaternal age is a major factor.Klinefelter’s syndrome: boys have underdeveloped testes; very low sperm count; language and learning development problems; breast developmentTurner’s syndrome: anatomically female; slow stunted growth; heart problems; poor cognitive skillsXXX: 1 in 1000; develop slowly; poor verbal skills; low intelligence; do poorly in schoolXYY: 1 in 1000; taller than average; large teeth; developmentally normal in other measures, including intelligence and aggression
17 Pregnancy and Prenatal Development The Mother’s Experience: First Trimester Zygote implants in the uterusCervix thickens and secretes mucus to protect embryoUterus shifts and puts pressure on bladderMissed period Breast enlargementCareRegular prenatal care critical at this timeProblemsEctopic pregnancy, bleeding, miscarriageWeek 0–Week 11:The zygote implants into the lining of the uterus. A chemical (HCG) is released in the urine that can help to diagnose pregnancy. The cervix thickens and secretes mucus, serving as a barrier and protecting the baby from bacteria. Prenatal care is critical because all of the baby’s organs are developing in the first eight weeks of pregnancy.
18 Pregnancy and Prenatal Development The Mother’s Experience: Second Trimester Weight gain“Showing”Fetal movements feltIncreased appetiteCareMonthly doctor visits continueUltrasoundProblemsGestational diabetes; Rh incompatibility; increased blood pressureMiscarriage; premature laborWeek 12–Week 24:weight gain; uterus expandsUltrasound can be used to monitor baby’s health. The risk of miscarriage drops.Fetus grows rapidly.Sex can be determined after Week 13.Fetal movement felt between Week 16 and 18.Prenatal care may detect gestational diabetes.
19 Pregnancy and Prenatal Development The Mother’s Experience: Third Trimester Colostrum in preparation for nursingEmotional connection between mother and baby growsFetal hiccups and thumb-sucking visible on sonogramFetus has regular activity and rest periodsCareWeekly visits (beginning in 32nd week)Ultrasound to assess position, pelvic exam to check cervical dilationProblemsIncreased blood pressure, bleeding, bladder infectionPremature laborWeek 25–Week 38:additional weight gain and abdominal enlargement
20 Pregnancy and Prenatal Development The Prenatal Experience: Germinal Stage Conception to implantation Blastocyst implants Specialization of cells needed to support developmentWeek 0–Week 2:Day 2: 1 cell becomes 4 and the zygote drifts down the fallopian tube; by day 12 it buries itself in the lining of the uterus; hormones are released to stop the woman’s menstrual cycle; a blastocyst is 60–100 cells that begin to specialize into different developmental support parts. Specialization of cells is needed to support development.PlacentaUmbilical cordYolk sacAmnion
21 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.2 to 8 weeks after conceptionForms foundations of all body organsNeural tube develops.All major organs and systems begin to develop.Many organs and systems begin to function.Week 3–Week 8:Neural tube (becomes the brain and spinal cord), heart, and kidneys develop during Week 3.Week 5:Arms and legs develop.Week 6:Brainwave activity starts.Week 7:penis development; skeletal system and bones begin to develop; eyelids seal shut to protect developing eyesWeek 8:Liver and spleen begin to function; digestive and urinary systems are functioning; organogenesis.
22 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 37Week 9–Week 38:Organs systems grow to become functioning during this period, especially the brain and lungs.Week 25:recognize the mother’s voiceWeek 24:age of viabilityWeek 37 onward:full-term status
23 Figure 3.3: Parts of the Neuron Structure of a Single NeuronCell 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 MalesMore physically activeHigher rates of miscarriageMore vulnerable to prenatal problemsFemalesMore sensitive to external stimulationMore rapid skeletal developmentMales: testosterone is produced during Weeks 4–8, helping with activity level as well as sexual organ development.Differences in physical development and coordination persist, with females remaining more advanced until adolescence.
25 Prenatal Sex Differences Some researchers suggest:Other researchers contend:MalesMore physically activeMore vulnerable to prenatal problemsFemalesMore sensitive to external stimulationMore rapid skeletal developmentSex differences in:Prenatal hormones linked to cross-gender variationsPrenatal problemsCan you guess what these might be?Prenatal hormones linked to cross-gender variations:Spatial abilityPhysical aggressionCommunication developmentSkeletal developmentPrenatal problems:Males more often spontaneously abortedMale more sensitive to mother’s marijuana useMales: testosterone is produced during Weeks 4–8, helping with activity level as well as sexual organ development.Differences in physical development and coordination persist, with females remaining more advanced until adolescence.
26 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.Ultrasound imaging helps to identify new information about fetal behavior. Fetal response to sounds and vibrations, as seen by changes in heart rate, head turns, and body movements, appears as early as Week 25. Fetuses can differentiate between familiar and novel stimuli by Week 32 or 33. Fetal learning is evidenced by the remembering of familiar rhymes, a Dr. Seuss story, the mother’s heartbeat, and the odor of amniotic fluid.
27 Figure 3.6 Correlations between Fetal Behavior and Brain Development
28 ??Questions To PonderYou 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 Development Teratogens See Figure 3.7 for timing of exposureFirst 8 weeks most dangerous exposure timeDuration and intensity exposure importantTeratogen: substance that can damage embryoGreatest damage during organ system’s most rapid development
31 Problems in Prenatal Development Teratogens: Drugs PrescriptionOver-the-counter drugsMarijuana, methamphetamine, and heroinCocaineTobaccoAlcoholSmoking: correlated with lower birth weight (half a pound lighter); higher rates of learning problems, anti-social behavior, and ADHDDrinking: FAS children are generally smaller, have facial changes, short, small heads, mild to severe mental retardation, and perceptual difficulties.Marijuana: most frequently abused drug; tremors and sleep problems; infants show little interest in their surroundings for up to two weeks.Heroin: can cause miscarriage, premature labor, early death, drug addiction; babies have high-pitched cries and suffer withdrawal.Cocaine: research is ambiguous due in part to the complex interaction between the drug and other teratogens to which the baby might be exposed.
32 Problems in Prenatal Development Teratogens: Maternal Diseases Rubella (“German measles”)HIVOther sexually transmitted diseasesRubella exposure during the first four to five weeks may cause deafness, cataracts, and heart defects.HIV can pass through the placenta or pass to the baby during a vaginal birth. One quarter of exposed infants become infected. AZT taken by mothers lowers the risk factor. Weakness in the immune system can lead to complications from other illnesses.Other sexually transmitted diseases:SyphilisGenital herpesGonorrheaCytomegalovirus
33 Problems in Prenatal Development Other Maternal Influences: Diet Folic acid deficienciesMalnutritionNeonate low birth weightBrain stuntingFetal deathMental illness in adulthoodDiet: folic acid deficiencies are associated with neural tube defects such as spina bifida.Malnutrition in the final three months is associated with low birth weight and even mental illnesses in adulthood.Affects the developing nervous system; brain stunting (weight and volume of the brain are reduced)
34 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.First pregnancies are occurring later—average age is now 25.1 years.Women over 35 have higher risks for pregnancy complications.Low-lying placentaPremature birthTeenage mothers have higher risks.May suffer from poverty and poor prenatal careChildren may exhibit learning and behavior problems in school.
35 Problems in Prenatal Development Other Maternal Influences: Chronic Illnesses Kinds of illnessDepressionEpilepsyDiabetesLupusPreventionMonitoring of mother and fetus necessary for most illnessesFetal–maternal specialist for high-risk patientDepression leads to premature labor; depressed mothers have difficulty with attachment issues.Fetal–maternal medicine helps to manage the effects of long-term illnesses including heart problems and diabetes.
36 Problems in Prenatal Development Environmental Hazards Detrimental effects of hazards may be reduced by:Limiting exposure to lead and mercuryAvoiding possible harmful chemicalsMercury: avoid consumption of contaminated fishLead: found in paint and pipes, lead crystalArsenic: pressure-treated lumberDental offices and outpatient surgery could be places which expose pregnant women to harmful gasses.Solvents: paint thinners, alcoholParasite-bearing substances: animal feces; undercooked meat, poultry, or eggs.Avoiding possible harmful chemicals:LeadArsenicAnesthetic gassesSolventsParasite-bearing substances
37 Problems in Prenatal Development Maternal Emotions Maternal stress and depression related to higher risks for fetusSocial support and counseling may help.Mixed information from researchMaternal stress and depression related to higher risks for fetusSeverely distressed mothers may produce fetuses who grow slowly, are premature, or are underweight.Social support and counseling may help.Mixed information from research
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 Neonate Birth Choices Things to considerLocation of birthBirth attendantsDrugs during labor and delivery“Natural childbirth”Location of BirthHome versus hospitalBirthing roomsBirth AttendantsCertified nurse-midwivesDrugs during labor and delivery“Natural childbirth”Lamaze method
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?
43 The Physical Process of Birth Labor: An Overview Stage 1ContractionsDilation of the cervixStage 2Actual delivery of the babyStage 3Delivery of the placenta and umbilical cord
46 The Physical Process of Birth Birth Complications: Cesarean Deliveries Why are Cesarean deliveries performed?Fetal distressBreech presentationBirth sizePoor progress during laborMother’s health and age concerns
47 The Physical Process of Birth Assessing the Neonate Apgar scaleBrazelton Neonatal Behavioral AssessmentWhy is neonatal assessment important?First month of lifeApgar scaleTable 3.7Brazelton Neonatal Behavioral AssessmentTracks development over two weeksResponses to stimuli and reflexes are checked.
48 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 risk of complications.
49 Assessing the Neonate Do LBW babies catch up? Development best assessed on individual basisTwo-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.First month of lifeApgar scaleTable 3.7Brazelton Neonatal Behavioral AssessmentTracks development over two weeksResponses to stimuli and reflexes are checked.