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Chapter 4 PRENATAL DEVELOPMENT AND BIRTH. FROM CONCEPTION TO BIRTH Phases of Prenatal Development –Period of the zygote: conception through implantation.

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Presentation on theme: "Chapter 4 PRENATAL DEVELOPMENT AND BIRTH. FROM CONCEPTION TO BIRTH Phases of Prenatal Development –Period of the zygote: conception through implantation."— Presentation transcript:


2 FROM CONCEPTION TO BIRTH Phases of Prenatal Development –Period of the zygote: conception through implantation –Period of the embryo: 3 rd -8 th week, organ formation, heart beat –Period of the fetus: 9 th week-birth

3 THE PERIOD OF THE ZYGOTE Blastocyst: cells –Embryo – inner layer of blastocyst –Protective/nourishing tissues – outer layer Implantation: –7-10 days after conception –Tapping mother’s blood supply through uterine wall –Only 25% successfully implant

4 Figure 4.1 The Period of the Zygote

5 PERIOD OF THE ZYGOTE Blastocyst: Support Structures –Amnion: watertight sac with amniotic fluid Cushioning against blows Temperature regulation Weightless environment for movement –Yolk sac: early blood cell production –Chorion: becomes lining of placenta –Allantois: forms umbilical cord

6 Figure 4.2 The embryo and its prenatal environment.

7 PERIOD OF THE ZYGOTE Purpose of the Placenta –Semipermeable Allowing nutrients and gasses to pass through Blood cells are too large –Site of all metabolic transactions sustaining the embryo

8 THE PERIOD OF THE EMBRYO Ectoderm (outer layer) –Nervous system –Skin –Hair Mesoderm (middle layer) –Muscles –Bones –Circulatory system

9 THE PERIOD OF THE EMBRYO Endoderm (inner layer) –Digestive system –Lungs –Urinary tract –Vital organs (pancreas, liver, etc.)

10 THE PERIOD OF THE EMBRYO Developmental Milestones –3 rd week – neural tube –4 th week – heart beat –7 th week – a rudimentary skeleton –7 th -8 th weeks – sexual development If male, the Y chromosome triggers a reaction to produce testes, otherwise ovaries result

11 Figure 4.3 A human embryo at 40 days.

12 THE PERIOD OF THE FETUS Third Month –Movement – cannot yet be felt by mother –Digestive system and excretory systems functioning –Reproductive system contains immature ova or sperm cells

13 Figure 4.4 Rate of body growth during the fetal period. Increase in size is especially dramatic from the ninth to the twentieth week. ADAPTED FROM MOORE & PERSAUD, 1993.

14 THE PERIOD OF THE FETUS Fourth-Sixth Months –Sucking, swallowing, breathing –Movements – felt by mother –Heart beat can be heard with stethoscope –Sweat glands functioning –Vernix – protects skin from chapping –Lanugo – fine hair helps vernix stick to skin –Visual and auditory senses are functional

15 THE PERIOD OF THE FETUS Seventh – Ninth Months –Age of viability weeks – survival outside the womb is possible –Weight is 4 pounds (at end of 7 th month) –9 th month – activity slows, sleep increases –Birth occurs

16 Table 4.1 Brief Overview of Prenatal Development

17 Table 4.1 Brief Overview of Prenatal Development (continued)

18 POTENTIAL PROBLEMS IN PRENATAL DEVELOPMENT Teratogen – any agent that can harm an embryo or fetus Effects of teratogens –Most serious when structure is forming –Susceptibility to harm is influenced by genetic makeup of mother and embryo –Same defect can be caused by different teratogens

19 POTENTIAL PROBLEMS IN PRENATAL DEVELOPMENT Effects of teratogens, continued –One teratogen can cause different defects –Longer exposure/higher dose, more harm –Father’s exposure may affect embryo –Long-term effects depend on postnatal environment –Some effects not apparent until later in life

20 Figure 4.5 The critical periods of prenatal development. Each organ or structure has a critical period when it is most sensitive to damage from teratogens. Dark band indicates the most sensitive periods. Light band indicates the time that each organ or structure is somewhat less sensitive to teratogens, although damage may still occur. ADAPTED FROM MOORE & PERSAUD, 1993.

21 TERATOGENS Diseases of the pregnant woman –Rubella (German measles) Blindness, deafness, cardiac abnormalities, mental retardation Most dangerous during 1 st trimester No woman should try to conceive unless they have had rubella or been immunized

22 TERATOGENS Toxoplasmosis – –Caused by eating undercooked meat, handling cat feces –Causes eye and brain damage during first trimester –Induces miscarriage later in pregnancy

23 Table 4.2 Common Diseases That May Affect an Embryo, Fetus, or Newborn

24 TERATOGENS Sexually Transmitted Diseases –Syphilis Cannot be transmitted to fetus until 18 th week Early treatment prevents harm Damages eyes, ears, bone, heart, brain Can result in miscarriage

25 TERATOGENS Sexually Transmitted Diseases –Genital Herpes Can cross placenta Most infections occur during birth Kills 33% of infected newborns Causes blindness, brain damage and other neurological problems in 25-30% Cesarean delivery prevents infecting newborn

26 TERATOGENS Sexually Transmitted Diseases –Acquired Immunodeficiency Syndrome (AIDS) Caused by HIV Passed through placenta, while giving birth, or while breast-feeding Only 25% of those at risk are infected ZDV reduces transmission by 70% 50% of HIV infected infants live past 6

27 TERATOGENS Drugs –Thalidomide Used to prevent nausea and vomiting Tested on animals and was “safe” Caused birth defects (for some) if taken during first 2 months of pregnancy –Eyes, ears, noses, hearts –Phocomelia – parts of limbs missing, feet or hands connected to torso

28 TERATOGENS Drugs –Aspirin – growth retardation, infant death –Ibuprofen – 3 rd trimester – pulmonary hypertension, prolonged delivery –Caffeine – miscarriage, low birth weight –Lithium – 1 st trimester – heart defects –Oral contraceptives – heart defects –Diethylstilbestrol (DES) – delayed effects in reproductive system, primarily female

29 TERATOGENS Drugs –Alcohol – compromises functioning of the placenta Fetal alcohol syndrome (FAS) –Microcephaly –Malformation of heart, limbs, joints and face –Hyperactivity, seizures, tremor –Lower IQ, major adjustment problems

30 TERATOGENS Alcohol –Fetal Alcohol Effects (FAE) Social drinking (1-3 per day) Greatest risk – binge drinking (5+) Slow physical growth, poor motor skills, attention difficulties, verbal learning difficulties Subnormal intellectual performance Father’s drinking may also be harmful

31 TERATOGENS Cigarette Smoking –Cleft lip –Abnormal lung functioning –Miscarriage –Low-birth-weight –Ectopic pregnancy – implantation in fallopian tube –Sudden Infant Death Syndrome –Higher concentration of nicotine in fetus

32 TERATOGENS Marijuana –Emotional regulation in males –Poorer reading/spelling at 10 years old –More depression/anxiety Narcotics (heroin, methadone) –60-80% born addicted –Breathing/swallowing coordination –Normal developmental progress by age 2, although boys remain vulnerable

33 TERATOGENS Cocaine –Miscarriage, premature birth –Sleep disturbances, very irritable –Lower IQ –Poor language development skills –Negative effects also due to Maternal vocabulary Home environment Exposure to additional teratogens

34 Table 4.3 Partial List of Drugs and Treatments Used by the Mother That Affect (or Are Thought to Affect) the Fetus or the Newborn

35 TERATOGENS Environmental Hazards –Radiation – death, mental retardation –Chemicals/pollutants Lead/mercury – deformities, mental retardation PCB’s – less neurologically mature –Prenatal and postnatal effects Father’s exposure also harmful

36 Figure 4.6 Average cognitive test performance at age nine, based on child’s level of exposure to PCB prenatally and through breast feeding. Light bars indicate children who were exposed to low levels of PCB, dark bars are children who were exposed to high levels of PCB.

37 MATERNAL CHARACTERISTICS Pregnant Woman’s Diet –Total weight gain pounds 1 st trimester malnutrition – miscarriage, spinal cord malformation 3 rd trimester malnutrition – low-birth- weight, small heads –Dietary supplements and stimulation can reduce effects of prenatal malnutrition

38 Figure 4.7 Incidence of infant mortality in the first 12 months for babies born to Dutch mothers who had experienced famine during World War II. ADAPTED FROM STEIN & SUSSER, 1976.

39 MATERNAL CHARACTERISTICS Pregnant Women’s Diet –Magnesium & Zinc – reduce complications –Folic acid – reduces Down Syndrome, spina bifida, anencephaly –Medical supervision is necessary, as excessive vitamin/mineral supplements can be harmful

40 MATERNAL CHARACTERISTICS Pregnant Woman’s Emotional Well-Being –Prolonged and severe emotional stress Stunted prenatal growth Premature delivery Irritable Irregular feeding, sleeping Causal relationship in animals

41 Figure 4.8 Percent of bath time infants spent fussing and crying. The figure compares infants whose mothers experienced high levels of cortisol (a hormone related to stress) to infants whose mothers experienced low levels of cortisol during pregnancy.

42 Figure 4.8 Percent of bath time infants spent fussing and crying. The figure compares infants whose mothers experienced high levels of cortisol (a hormone related to stress) to infants whose mothers experienced low levels of cortisol during pregnancy. (continued)

43 MATERNAL CHARACTERISTICS Pregnant Women’s Emotional Well Being –Prolonged stress Stress hormones – impede oxygen and nutrients to fetus Weaken immune system Linked to poor eating, smoking, drug and alcohol use – all harm fetus Counseling to manage/reduce stress Moderate levels may aid development

44 MATERNAL CHARACTERISTICS Pregnant Woman’s Age – is optimal –15 years old and younger Impoverished backgrounds –Poor nutrition, high stress, little prenatal care Little risk if good prenatal care is present –Older than 35 Increased risk of miscarriage Risks not reduced by prenatal care

45 BOX FOCUS ON RESEARCH: FETAL PROGRAMMING Fetal Programming Theory – brain and other systems are programmed in a manner that is adaptive for the uterine environment –Persists at birth, but what’s adaptive in the uterus may not be after birth –Focus is on subtle changes in metabolism, endocrine and autonomic functions –Result may be increased susceptibility to diseases in adulthood, like diabetes

46 PREVENTION OF BIRTH DEFECTS 95% of newborns are normal Many of remaining 5% have minor congenital problems that are temporary or correctable Each pregnancy is different –Genetic makeup –Prenatal environment

47 Table 4.4 Reducing Likelihood of Congenital Disorders.

48 BIRTH AND THE PERINATAL ENVIRONMENT Perinatal environment – environment surrounding birth –Medications –Delivery practices –Social environment

49 THE BIRTH PROCESS First stage of labor –Contractions minutes apart –Cervix fully dilates Second stage of labor – delivery –Head passes through cervix –Baby emerges from body Third stage of labor – afterbirth –Placenta expelled from body

50 Figure 4.9 The three stages of childbirth.

51 THE BABY’S EXPERIENCE Stressful, but assists with breathing Baby’s Appearance - 20 inches long, pounds, bluish, a bit misshapen Assessing the Baby’s Condition –Apgar test Heart rate, respiratory effort, muscle tone, color, reflex irritability Scored 0-10 (0-2 each) 7+ good, 4 and lower needs attention

52 Table 4.5 The Apgar Test

53 THE BABY’S EXPERIENCE Assessing the Baby’s Condition –Neonatal Behavioral Assessment Scale Several days after birth 20 inborn reflexes Reactions to comforting and social stimuli Unresponsiveness may indicate neurological problems Can be a parent teaching tool

54 LABOR AND DELIVERY MEDICATION Some medication used by 95% of mothers –Reduce pain, induce contractions, relax the mother –Can reduce the ability to push effectively –Can make babies lethargic and inattentive –Drugs in appropriate doses can increase comfort without disrupting delivery

55 BOX 4.2 – APPLYING RESEARCH TO YOUR LIFE: VARIATIONS IN BIRTHING PRACTICES Pokot of Kenya – community celebration Uttar Predesh in India – shameful, disgusting U.S. typically a hospital procedure –Natural / prepared childbirth: focus is on support, relaxation – reduces medication –Home births – shorter labors, less meds, safe if smooth pregnancy, trained midwife –Alternative birthing centers – homelike setting in hospital

56 THE SOCIAL ENVIRONMENT SURROUNDING BIRTH Mother’s experience –First 6-12 hours – sensitive period for emotional bonding (not essential) –Maternity blues – 40-60% of mothers –Postpartum depression – 10% of mothers Should seek professional help Depression affects outcomes of both mother and infant

57 THE SOCIAL ENVIRONMENT SURROUNDING BIRTH The Father’s experience –Engrossment – intense fascination, desire to touch, hold and caress –Early contact with newborn can make father feel closer to partner, positive support for mother

58 POTENTIAL PROBLEMS AT BIRTH Anoxia – oxygen deprivation –Umbilical cord becomes tangled –Breech position –Placenta separation –RH factor incompatibility – now preventable –Can cause neurological damage, permanent disabilities –Increased risk of adult heart disease

59 POTENTIAL PROBLEMS AT BIRTH Complications of Low Birth Weight –Preterm – born more than 3 weeks early, but appropriate weight for time in womb –Small for date – underweight due to slow fetal growth – greater risk than preterm Causes include smoking, drug use, stress, lack of prenatal care, multiple births, social support

60 [ Figure Gestational age at birth for singletons, twins, and triplets.

61 POTENTIAL PROBLEMS AT BIRTH Short-term Consequences of Low Birth Weight –40-50% weighing less than 2.2 pounds die –Brain development and neural pattern formation in preterm infants differs –Breathing difficulty due to lack of surfactin, or respiratory distress syndrome –Spend time in isolettes –Can be frustrating to care for

62 POTENTIAL PROBLEMS AT BIRTH Interventions for Preterm Infants –Early acquaintance programs – touching, rocking, talking, are developmentally beneficial –Parents can be taught how to be sensitive and responsive to preterm infants –Combined with stimulating day care programs help, improves cognitive growth and reduces behavioral disturbances

63 POTENTIAL PROBLEMS AT BIRTH Long-term Consequences of Low Birth Weight –Depends on postnatal environment Stimulating home, very good Less stable home or being economically disadvantaged –Smaller, emotional problems –Deficits in intellectual/academic performance

64 Figure Age trends in intellectual development for low-birth-weight twins from middle-class (high SES) and lower socioeconomic (low SES) backgrounds. ADAPTED FROM WILSON, 1985.

65 REPRODUCTIVE RISK AND CAPACITY FOR RECOVERY Werner & Smith – Kauai Longitudinal Study –At birth, 16% severe complications, 31% mild –Age 2 – severity predicted developmental progress, but emotional support and educational stimulation improved outcomes –Age 10 – severity not very predictive, home environment now predictive

66 APPLYING DEVELOPMENTAL THEMES TO PRENATAL DEVELOPMENT AND BIRTH Active child – moves, practices in womb Nature/nurture interaction – effects of teratogens Qualitative changes – stages of birth Quantitative changes – fetal development Holistic nature of development – prenatal development affects all future development; social support during birth has consequences for future development

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