Chapter 4 PRENATAL DEVELOPMENT AND BIRTH

1. Chapter 4 PRENATAL DEVELOPMENT AND BIRTH

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

3. THE PERIOD OF THE ZYGOTE • Blastocyst: 60-80 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 • 3rd week – neural tube • 4th week – heart beat • 7th week – a rudimentary skeleton • 7th-8th 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 - 22-28 weeks – survival outside the womb is possible • Weight is 4 pounds (at end of 7th month) • 9th 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 1st 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 18th 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 – 3rd trimester – pulmonary hypertension, prolonged delivery • Caffeine – miscarriage, low birth weight • Lithium – 1st 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 25-35 pounds • 1st trimester malnutrition – miscarriage, spinal cord malformation • 3rd 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 – 16-35 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 4.1 - 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 10-15 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.