This chapter discusses prenatal development from conception through birth. It covers genetics and inheritance, the stages of prenatal development from embryo to fetus, potential problems during pregnancy like maternal diseases and environmental hazards, and assessing the health of the neonate at birth. Factors that influence development include genes, environment, maternal health, nutrition, and exposure to teratogens. The chapter also examines the physical process of birth and potential complications.

1. Chapter 3:
Prenatal Development and Birth

2. In This Chapter

3. Conception and Genetics
Chromosomes, DNA, and Genes
Process of conception
 Ovum
 Sperm
 Zygote
Chromosomes
 DNA
 Genes

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

5. Conception and Genetics
Multiple 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 Genetics
How 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 Genetics
Other Types of Inheritance
Genomic imprinting: Some genes
biochemically marked at time ova and sperm
develop
Mitochondrial inheritance: Genes in
mitochondria

11. 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?

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.

13. Genetic Disorders
Sex-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 Errors
Trisomies and Monosomies
Trisomies: Three chromosomes, rather than
usual pair
Monosomies: Absence of one member of
chromosome pair

16. 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

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

18. 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

19. 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

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

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.

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 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:
 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?

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.

27. Figure 3.6 Correlations between Fetal Behavior and
Brain Development

28. 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?
Questions To PonderQuestions To PonderQuestions To PonderQuestions To Ponder

29. Teratogen:
substance that can
damage embryo
See Figure 3.7 for
timing of
exposure
Greatest damage
during organ
system’s most rapid
development
First8weeksmost
dangerous
exposuretime
Durationand
intensityexposure
important
Problems in Prenatal Development
Teratogens

30. Figure 3.7 Timing of Teratogen Exposure

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

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

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

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.

35. 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

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

37. Problems in Prenatal Development
Maternal 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 Neonate
Birth 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.ht

43. 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

44. Figure 3.9 The Three Stages of Labor

45. Figure 3.9 The Three Stages of Labor

46. 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

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

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
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.