1. Prenatal Development and Birth
Chapter 3:
Prenatal Development and Birth

2. In This Chapter Conception and genetics
Genetic and chromosomal disorders
Pregnancy and prenatal development
Problems in prenatal development
Birth and the neonate

3. Conception and Genetics Chromosomes, DNA, and Genes
Process of conception
Ovum
Sperm
Zygote
Chromosomes
DNA
Genes
Conception and Genetics
The 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
Chromosomes
Autosomes
Sex chromosomes (X, Y)
Chromosomal differences
Androgens and SRY gene
Gonad development
Congenital adrenal hyperplasia

5. Conception and Genetics Multiple Births
Twins
Identical (monozygotic)
Fraternal (dizygotic)
Semi-identical (different genes from father)
Conception and Genetics
Fraternal 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 blueprint
Phenotype: Observable characteristics
Dominant–recessive pattern
Polygenic inheritance
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.
Dominant–recessive pattern
Dominant genes always express their characteristics.
Recessive genes come in pairs to express their characteristics.
Polygenic Inheritance
Many 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 develop
Mitochondrial inheritance: Genes in mitochondria
Polygenic: many genes influence the phenotype.
Skin color: 3 genes that may blend dark and light colored genes
Eye color: variations that offer multiple color possibilities
Height: 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 environment
Five general principles (Rutter et al.)
In what ways have genetics and environment integrated to influence your development?
Rutter principles
Individual differences in reactivity to environment
Two-way interplay between people and environment
People-environment interplay considered in ecological framework
People 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 disease
Tay-Sachs disease
Disorders caused by dominant genes:
Huntington’s disease
Autosomal disorders:
PKU: common; caused by lack of the ability to metabolize a protein, phenylalanine
Sickle-cell anemia: defect creates sickle-shaped red blood cells; offers protection against malaria
Tay-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 chromosome
Red–Green Colorblindness
Hemophilia
Fragile X Syndrome
Boys 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 pair
Trisomy 21: Down syndrome
Mental retardation
Distinctive facial features
Physical abnormalities
Maternal age is a major factor.

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
Trisomy 21: Down syndrome
Mental retardation
Distinctive facial features
Physical abnormalities
Maternal age is a major factor.
Klinefelter’s syndrome: boys have underdeveloped testes; very low sperm count; language and learning development problems; breast development
Turner’s syndrome: anatomically female; slow stunted growth; heart problems; poor cognitive skills
XXX: 1 in 1000; develop slowly; poor verbal skills; low intelligence; do poorly in school
XYY: 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 uterus
Cervix thickens and secretes mucus to protect embryo
Uterus shifts and puts pressure on bladder
Missed period Breast enlargement
Care
Regular prenatal care critical at this time
Problems
Ectopic pregnancy, bleeding, miscarriage
Week 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 felt
Increased appetite
Care
Monthly doctor visits continue
Ultrasound
Problems
Gestational diabetes; Rh incompatibility; increased blood pressure
Miscarriage; premature labor
Week 12–Week 24:
weight gain; uterus expands
Ultrasound 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 nursing
Emotional connection between mother and baby grows
Fetal hiccups and thumb-sucking visible on sonogram
Fetus has regular activity and rest periods
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
Week 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 development
Week 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.
Placenta
Umbilical cord
Yolk sac
Amnion

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 conception
Forms foundations of all body organs
Neural 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 eyes
Week 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 37
Week 9–Week 38:
Organs systems grow to become functioning during this period, especially the brain and lungs.
Week 25:
recognize the mother’s voice
Week 24:
age of viability
Week 37 onward:
full-term status

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
Males: 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:
Males
More physically active
More vulnerable to prenatal problems
Females
More sensitive to external stimulation
More rapid skeletal development
Sex differences in:
Prenatal hormones linked to cross-gender variations
Prenatal problems
Can you guess what these might be?
Prenatal hormones linked to cross-gender variations:
Spatial ability
Physical aggression
Communication development
Skeletal development
Prenatal problems:
Males more often spontaneously aborted
Male more sensitive to mother’s marijuana use
Males: 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 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 Development Teratogens
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 Development Teratogens: Drugs
Prescription
Over-the-counter drugs
Marijuana, methamphetamine, and heroin
Cocaine
Tobacco
Alcohol
Smoking: correlated with lower birth weight (half a pound lighter); higher rates of learning problems, anti-social behavior, and ADHD
Drinking: 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”)
HIV
Other sexually transmitted diseases
Rubella 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:
Syphilis
Genital herpes
Gonorrhea
Cytomegalovirus

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
Diet: 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 placenta
Premature birth
Teenage mothers have higher risks.
May suffer from poverty and poor prenatal care
Children may exhibit learning and behavior problems in school.

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
Depression 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 mercury
Avoiding possible harmful chemicals
Mercury: avoid consumption of contaminated fish
Lead: found in paint and pipes, lead crystal
Arsenic: pressure-treated lumber
Dental offices and outpatient surgery could be places which expose pregnant women to harmful gasses.
Solvents: paint thinners, alcohol
Parasite-bearing substances: animal feces; undercooked meat, poultry, or eggs.
Avoiding possible harmful chemicals:
Lead
Arsenic
Anesthetic gasses
Solvents
Parasite-bearing substances

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
Maternal stress and depression related to higher risks for fetus
Severely distressed mothers may produce fetuses who grow slowly, are premature, or are underweight.
Social support and counseling may help.
Mixed information from research

38. Fetal Assessment and Treatment
Ultrasonography
Chorionic Villus Sampling (CVS)
Amniocentesis
Alpha-Fetoprotein Blood Test
Fetoscopy

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”
Location of Birth
Home versus hospital
Birthing rooms
Birth Attendants
Certified nurse-midwives
Drugs 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 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?
First month of life
Apgar scale
Table 3.7
Brazelton Neonatal Behavioral Assessment
Tracks development over two weeks
Responses 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 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.
First month of life
Apgar scale
Table 3.7
Brazelton Neonatal Behavioral Assessment
Tracks development over two weeks
Responses to stimuli and reflexes are checked.