Prenatal Development and Birth - learning.hccs.edu

Prenatal Development and Birth

Chapter 3:

IN THIS CHAPTER

• Conception and Genetics

• Genetic and Chromosomal Disorders

• Pregnancy and Prenatal Development

• Problems In Prenatal Development

• Birth and The Neonate

LEARNING OBJECTIVES

3.1 What are the characteristics of the zygote?

3.2 In what ways do genes influence development?

3.3 What are the effects of the major dominant, recessive, and sex-linked diseases?

3.4 How do trisomes and other disorders of the autosomes and sex chromosomes affect development?

3.5 What are the characteristics of each trimester of pregnancy?

3.6 What happens in each stage of prenatal development?

3.7 How do male and female fetuses differ?

3.8 What behaviors have scientists observed in fetuses?

3.9 How do teratogens affect prenatal development?

LEARNING OBJECTIVES (con’t)

3.10 What are the potential adverse effects of tobacco, alcohol, and other drugs on prenatal development?

3.11 What risks are associated with teratogenic maternal diseases?

3.12 What other maternal factors influence prenatal development?

3.13 How do physicians assess and manage fetal health?

3.14 What kinds of birth choices are available to expectant parents?

3.15 What happens in each of the three stages of labor?

3.16 What do physicians learn about a newborn from the Apgar and Brazelton scales?

3.17 Which infants are categorized as low birth weight, and what risks are associated with this status?

CONCEPTION AND GENETICS

Chromosomes, DNA, and Genes

Process of Conception

▪ Ovum

▪ Sperm

▪ Zygote

Chromosomes

▪ DNA

▪ Genes


Sex Determination

Chromosomes

▪ Autosomes

▪ Sex chromosomes (X, Y)

Chromosomal Differences

▪ Androgens and SRY gene

▪ Sex chromosomes (X, Y)

▪ Gonad development


Multiple Births

Twins

• Identical (monozygotic)

• Fraternal (dizygotic)

• Semi-identical (different genes from father)

STOP AND THINK!

Your textbook notes an increase in multiple births

over the past thirty years.

Why has this occurred?


How Genes Influence Development

Genotype: genetic blueprint

Phenotype: observable characteristics

• Dominant–recessive pattern

• Polygenic inheritance

Twins in Genetic Research

Comparison of identical and fraternal twins has been been used for many decades to exam the role of heredity in human development.

Identical twins are more similar than fraternal twins on measures of emotionality, activity, sociability, and intelligence

Yet correlations that twins researchers have found are less than +1.00, even for identical twins who grow up in the same home.

This offers strong evidence that psychological traits are clearly influenced by heredity. This might not be true for physical traits.

Can you apply this information?

Critical Analysis

1. Fraternal twins are no more genetically similar

than non-twin siblings, yet the IQs of fraternal twins

are more strongly correlated than those of non-twin

brothers and sisters. What explanations can you

think of to explain this difference?

2. The term environment is extremely broad. What

are some of the individual variables that comprise

an individual’s environment?

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?

THE GENETICS OF HAIR TYPE

GENETIC SOURCES OF NORMAL TRAITS


Other Types of Inheritance

• Genomic imprinting: some genes

biochemically marked at time ova and sperm

develop

• Mitochondrial inheritance: genes in

mitochondria


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?

GENETIC DISORDERS

Autosomal Disorders

Autosomal gene: one of twenty-two pairs of

autosomes that are involved in sex determination

Autosomal recessive disorder: two copies of the

abnormal gene must be present for the disease or

trait to develop.

Autosomal dominant disorder: abnormal gene

from one parent sufficient to inherit disease or trait

See Table 3.2 (p. 55) for a summary of some

genetic disorders.

SOME GENETIC DISORDERS

SEX-LINKED INHERITANCE

GENETIC DISORDERS

Sex-Linked Disorders

Sex-linked disorders: caused by recessive gene

on X chromosome

Red–Green Colorblindness

Hemophilia

Fragile X Syndrome

STOP AND THINK…

Why do boys have Fragile X Syndrome more often

than girls do?

CHROMOSOMAL ERRORS

Trisomies and Monosomies

Trisomies: three chromosomes, rather than the

usual pair

Monosomies: absence of one member of

chromosome pair

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

Zygote implants in the uterus

Cervix thickens and secretes mucus to

protect embryo

Uterus shifts and puts pressure on

bladder

Missed periodBreast enlargement

PREGNANCY AND PRENATAL DEVELOPMENT

The Mother’s Experience: First Trimester

Care

• Regular prenatal care critical at this time

Problems

• Ectopic pregnancy, bleeding, miscarriage

Weight gain “Showing”Fetal

movements feltIncreased appetite


The Mother’s Experience: Second Trimester

Care

▪ Monthly doctor visits continue

▪ Ultrasound

Problems

▪ Gestational diabetes; Rh incompatibility; increased

blood pressure

▪ Miscarriage; premature labor

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


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


The Prenatal Experience: Germinal Stage

Conception to Implantation

• Blastocyst implants

• Specialization of cells needed to support

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.


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

PARTS OF THE NEURON

Structure of a Single

Neuron

• Cell bodies first to

develop (weeks 12–24).

• Axons and dendrites

develop later (especially

final 12 weeks).

• Axons continue to

increase in size and

complexity after birth.

Figure 3.3. Parts of the Neuron

FETAL DEVELOPMENT

Figure 3.4 Fetal yawning appears between the 10th and 15th week. Its presence signals the beginning of sleep stages in the fetal brain.

Figure 3.5 Glial cells that develop during the last few months of prenatal development hold neurons together and give form and structure to the fetal brain.(Source: Brown, Estroff, & Barnenott, 2004.)

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

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?

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.

Teratogen: substance that can

damage embryo

See Figure 3.7 for timing of exposure

Greatest damage during organ

system’s most rapid development

PROBLEMS IN PRENATAL DEVELOPMENT

TERATOGENS

THE TIMING OF TERATOGEN EXPOSURE


Teratogens: Maternal Diseases

• Cancer

• Toxoplasmosis

• Chicken pox

• Parvovirus

• Hepatitis B

• Chlamydia

• Tuberculosis


Teratogens: Drugs

• Inhalants

• Accutane/vitamin A

• Streptomycin

• Penicillin

• Tetracycline

• Diet pills


Teratogens: Drugs

• Prescription

• Over-the-counter drugs

• Marijuana, methamphetamine, and heroin

• Cocaine

• Tobacco

• Alcohol


Other Maternal Influences: Diet

• Folic acid deficiencies

• Malnutrition

▪ Neonate low birth weight

▪ Brain stunting

▪ Fetal death

▪ Mental illness in adulthood


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.


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


Environmental Hazards

Detrimental effects of hazards may be reduced

by:

• Limiting exposure to lead and mercury

• Avoiding possible harmful chemicals


Maternal Emotions

Maternal stress and depression are related to

higher risks for the fetus.

• Social support and counseling may help.

• Mixed information from research

FETAL ASSESSMENT AND TREATMENT

Ultrasonography

Chorionic Villus Sampling (CVS)

Amniocentesis

Alpha-Fetoprotein Blood Test

Fetoscopy

CAN YOU IDENTIFY EACH METHOD?

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?

BIRTH AND THE NEONATE

Birth Choices

Things to Consider

• Location of birth

• Birth attendants

• Drugs during labor and delivery

• “Natural childbirth”

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.html

http://www.childbirth.org/interactive/ibirthplan.html

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

THE THREE STAGES OF LABOR

THE THREE STAGES OF LABOR


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


Assessing the Neonate

• Apgar scale

• Brazelton Neonatal Behavioral Assessment

Why is neonatal assessment important?

THE APGAR SCALE

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 the risk of complications.

ASSESSING THE NEONATE

Do LBW babies catch up?

• Development is best assessed on an individual

basis.

• Two-thirds to three-fourths of preterm infants

catch up by school entrance.

• Lowest birth weight and earlier gestational age

are associated with long-term developmental

delays.

SINGING TO PRETERM INFANTS

The use of music by NICU staff and parents to

support the development of preterm infants is

an active area of research in the emerging field

of music therapy.

• Ate more and gained weight faster

• Discharged earlier

• Higher oxygen saturation levels

• Stronger infant–parent emotional bond

Reflection

1. How could the research on singing to preemies

be put into practice in neonatal intensive care

units in nondisruptive ways?

2. If you were responsible for helping parents of

newborns understand the value of singing to

their babies, how would you explain the relevant

research to them?

WHEN DO PRETERM INFANTS CATCH UP WITH

FULL-TERM INFANTS?

Although many premature infants catch up with

their peers by the time they go to school,

developmentalists caution that the development of

preterm children is best assessed on a case-by-case

basis.

Several factors influence development.

• Birth weight

• Gestational weight

• Parental responses

You Decide

Decide which of these two statements you most

agree with and think about how you would defend

your position:

1. Two-thirds to three-quarters of premature infants

catch up to their peers by the time they go to

school, so it’s best to adopt a “wait and see”

attitude toward your child’s development before

attempting to influence it in order to avoid

pushing the child beyond his or her limits.

You Decide

2. Both parental responses and realistic

expectations are important in parenting a child

who was born prematurely, so it’s best to do

everything possible to enhance your child’s

development without expecting him or her to

develop in exactly the same way as a child who

was born at term.

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Prenatal Development and Birth - learning.hccs.edu