© 2009 Allyn & Bacon Publishers Prenatal Development And Birth 3 This multimedia product and its contents are protected under copyright law. The following

© 2009 Allyn & Bacon Publishers

Prenatal Development And Birth

3

This multimedia product and its contents are protected under copyright law. The following are prohibited by law:• any public performance or display, including transmission of any image over a network;• preparation of any derivative work, including the extraction, in whole or part, of any images;• any rental, lease, or lending of the program.


• The Process of Conception– Ovum– Sperm

• The Journey of Sperm toward Ovum

• Chromosomes– DNA– Genes– X and Y chromosomes

Conception and Genetics


• Twins– Identical– Fraternal– Semi-identical (different genes from father)

• Twins in genetic research

• Increases in multiple births



• Genotype — the genetic blueprint

• Phenotype — observable characteristics

• 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



Figure 3.1 The Genetics of Hair Type


• Genomic Imprinting– Some genes biochemically marked at the

time ova and sperm develop

• Mitochondrial Inheritance– Genes in the mitochondria, fluid

surrounding the nucleus of the ovum



• Genetics and the environment– Differ in their reactivity– Two-way interplay– Ecological framework

• People actively process their experiences

• People shape and select their experiences

Conception and GeneticsMulti-Factorial Inheritance


• Non-sex-lined genes

• Disorders caused by recessive genes– Phenylketonuria (PKU)– Sickle-cell disease– Tay-Sachs disease

• Disorders caused by dominant genes– Huntington’s disease

Genetic DisordersAutosomal Disorders


• Red–green colorblindness

• Hemophilia

• Fragile-X syndrome

• Caused by recessive gene on X chromosome

• Boys suffer more often than girls

Genetic DisordersSex-linked Disorders


Figure 3.2 Sex-linked Inheritance


• Chromosomal Errors– Too many or too few chromosomes

• Trisomy 21 — Down Syndrome• Mental retardation

• Distinctive facial features

• Physical abnormalities

• Maternal age is a major factor

Chromosomal ErrorsTrisomies


• XXY — Klinefelter’s syndrome

• XO — Turner’s syndrome

• XXX — girls with an extra X

• XYY — boys with an extra Y

Chromosomal ErrorsSex Chromosome Anomalies


• The zygote implants in the uterus

• The cervix

• Prenatal care critical at this time

• Ectopic pregnancy in fallopian tube rather than uterus– Threatens life and future fertility

Pregnancy and Prenatal DevelopmentThe Mother’s Experience: First Trimester


• Fetus grows rapidly

• Sex can be determined after week 13

• Fetal movement felt between week 16 and 18

• Prenatal care may detect gestational diabetes

• Risk of miscarriage drops

Pregnancy and Prenatal DevelopmentThe Mother’s Experience: Second Trimester


• Colostrum in preparation for nursing• Emotional connection between mother and

baby grows• Fetal hiccups and thumb sucking visible on

sonogram• Fetus has regular periods activity and rest• Toxemia

– Sudden high blood pressure

Pregnancy and Prenatal DevelopmentThe Mother’s Experience: Third Trimester


• From conception to implantation• Blastocyst implants • Specialization of cells needed to support

development – Placenta– Umbilical cord– Yolk sac– Amnion

3 Stages of Prenatal DevelopmentThe Germinal Stage: The Zygote


• Forms the foundations of all body organs

• Neural tube develops

• All major organs and systems begin to develop

• Many organs and systems begin to function

3 Stages of Prenatal DevelopmentThe Embryonic Stage


• Growth from 1/4 ounce and 1 inch to 7 pounds and 20 inches in length

• Refinement of all organ systems

• Neuronal proliferation

• Age of viability—week 24

• Full term status—week 37 onward

3 Stages of Prenatal DevelopmentThe Fetal Stage


Figure 3.3 Parts of the Neuron


• Males are:– More physically active– Higher rates of miscarriage– More vulnerable to prenatal problems

• Females are: – More sensitive to external stimulation– More rapid skeletal development

Prenatal Sex Differences


• Fetuses can differentiate between familiar and novel stimuli

• Newborns can remember prenatal stimuli and react accordingly

• Very active fetuses tend to be active children who can be labeled “hyperactive” later on

Prenatal Behavior


Figure 3.6 Correlations between Fetal Behavior and Brain Development


Questions to Ponder

• You are told by a genetic counselor that you have 25% 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?


• Substances that can damage an embryo

• Each organ system most vulnerable to harm when its development is most rapid (Figure 3.7)

• The first 8 weeks the most dangerous

• Duration and intensity of teratogen exposure important

Problems in Prenatal DevelopmentTeratogens


Figure 3.7 Timing of Teratogen Exposure


• Prescription

• Over the Counter

• Marijuana and Heroin

• Cocaine

• Smoking

• Alcohol use– Fetal Alcohol Syndrome

Problems in Prenatal DevelopmentTeratogens: Drugs


• Rubella (“German measles”)

• HIV

• Other sexually transmitted diseases– Syphilis– Genital herpes– Gonorrhea– Cytomegalovirus

Problems in Prenatal DevelopmentTeratogens: Maternal Diseases


• Diet – Folic acid deficiencies

– Malnutrition• Low birth weight

• Brain stunting– Reduced weight and volume of the brain

• Fetal death

Problems in Prenatal DevelopmentOther 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 • May suffer from poverty and poor prenatal care• Children may exhibit learning and behavior problems in

school



• Chronic Illnesses– Depression can slow fetal growth– Epilepsy – Diabetes

• Most medical conditions must be monitored to support health of the mother and developing fetus



• Limiting exposure to mercury

• Avoiding possible harmful chemicals– Lead– Arsenic– Anesthetic gasses– Solvents– Parasite-bearing substances

Problems in Prenatal DevelopmentEnvironmental Hazards


• Stress– Can change hormone levels

• Mixed information from research

• Severely distressed mothers produce fetuses who grow slowly

• Social support and counseling may help.

Problems in Prenatal DevelopmentMaternal Emotions


• Ultrasonography

• Chorionic Villus Sampling

• Amniocentesis

• Alpha-fetoprotein test

• Fetoscopy

Fetal Assessment and Treatment


Figure 3.8 Two Methods of Prenatal Diagnosis


• Location of Birth– Home versus hospital

– Birthing rooms

• Birth Attendants– Certified nurse-midwives

• Drugs during Labor and Delivery

• “Natural childbirth”– Lamaze Method

Birth Choices


• Stage 1– Contractions– Dilation of the cervix

• Stage 2– Actual delivery of the baby

• Stage 3– Delivery of the placenta and umbilical cord

The Physical Process of BirthLabor


Figure 3.9 The Three Stages of Labor



• Cesarean Deliveries– Fetal Distress– Breech presentation– Birth size– Poor progress during labor– Health and age concerns

The Physical Process of BirthBirth Complications


Figure 3.10 Duration of Labor in First and Second Births


• First month of life• Apgar Scale

– Table 3.7

• Brazelton Neonatal Behavioral Assessment– Tracks development over 2 weeks– Responses to stimuli and reflexes are

checked

The Physical Process of BirthAssessing the Neonate


• LBW – below 2,500 grams (5.5 pounds)

• Preterm – mostly born before week 38

• Small-for-date neonates

• Respiratory distress syndrome

• Adequate parental education and support reduces risk of complications

Low Birth Weight Babies (LBW)

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© 2009 Allyn & Bacon Publishers Prenatal Development And Birth 3 This multimedia product and its contents are protected under copyright law. The following