Chapter 3

Conception, Prenatal Development, and Birth

In this chapter. . .

What happens during the first nine months of development? Will the baby be normal?

What should parents do during pregnancy to optimize the baby’s health? What happens during the birth process?

Stages of Prenatal Development

• http://thevisualmd.com/videos/result/from_conception_to_birth

Stage DurationGerminal Conception to 2 weeks

Embyronic 2-8 weeksFetal 8 weeks to birth

Fertilization

• Process by which sperm and ovum combine to create a single cell—zygote

• What happens when a woman ovulates?

• Where is sperm produced?

• How does sperm get to the ovum for fertilization?

• When and where does fertilization take place?

Multiple Births

• Monozygotic (MZ) – One egg – One sperm – Identical Twins – Share 100% of genes

• Dizygotic (DZ) – Two eggs – Two sperm – More common – Fraternal Twins – Share 50% of genes – just like

non-twin siblings • Semi-identical• Superfetation--

Women Got Pregnant Twice - YouTube

Conception and the Zygote:The First Two Weeks

• Gestation – period from conception to birth

• Within hours of conception, the sperm and egg create a zygote.

–End of first week differentiation of cells begins.

–During second week implantation occurs.

Germinal Stage: Conception to 2 weeks

Embryonic Stage: 2-8 weeks

Ectoderm

• Skin• Nerves• Sense organs

Mesoderm

• Muscle• Bones• Circulatory system• Some organs

Endoderm

• Digestive system• Lungs• Urinary tract• Glands

• Specialized layers of cells• Organs and major body systems

develop rapidly – Respiratory – Digestive – Nervous

• 3 ½ weeks—brain begins to form

• Neurogenesis begins

• Risk of spontaneous abortion

Fetal Stage: 8 weeks to Birth

• Organs, muscles, nervous system more organized, connected

• Size increases• Cephalocaudal/• Proximodistal Principles • Finishing touches –

toenails, eyelids • Appearance of bone • Fetal Development Picture

s Slideshow: Photos Month-by-Month by WebMD

Figure 3.3—Sensitive Periods in Prenatal Development

Prenatal Development: Ultrasound Imaging

• http://www.youtube.com/watch?v=PN3e7nyExqc&feature=fvsr

• http://www.youtube.com/watch?v=PN3e7nyExqc

Chromosomal Abnormalities

• Typically occur because of errors in cell division

• Result is extra or missing chromosome

• http://www.biology.iupui.edu/biocourses/N100/2k2humancsomaldisorders.html

Karyotype of Down Syndrome

Dominant/Recessive Inheritance

• Alleles

• Every person inherits a pair of alleles for a particular characteristic from each parent

• What does it mean to be homozygous for a trait?

• Heterozygous?

• When person inherits contradictory alleles for a trait, which will be expressed, dominant or recessive?

• When person inherits 2 recessive alleles what will be expressed?

Genetic Abnormalities

• Defects transmitted by dominant or recessive inheritance• Usually normal genes are dominant over genes carrying abnormal traits• Sometimes gene for an abnormal trait is dominant• Examples—Huntington’s Disease, achondroplasia (form of dwarfism)• Recessive defects are expressed only if a child receives the same recessive

abnormal gene from each parent• Examples—sickle-cell anemia, Tay-Sachs disease

Dominant Inheritance of a Disease--e.g., Huntington’s disease (brain disorder that affects ability to talk, think, move), achondroplasia (a form of dwarfism)

Recessive Inheritance of a Disease—e.g., Tay-Sachs disease (lack of enzyme to break down fatty waste in brain cells resulting in loss of motor and mental functions and eventually death), sickle cell anemia (abnormal hemoglobin that result in sickle shaped red blood cells that block small

blood vessels resulting in anemia, jaundice, gallstones, pain, lung tissue damage, etc.)

Prenatal Assessment

• Amniocentesis• Chorionic villi• False positives• False negatives

Stages of Childbirth

• First stage—usually the longest—12 hours or more, especially for first child

• What happens during the first stage of childbirth?

Second Stage of Labor

• Usually lasts up to one hour

• What is happening with the contractions?

• Where is the baby moving to?

• When does the second stage end?

• What happens if this stage goes on for too long?

Second Stage of Labor

• http://www.evtv1.com/player.aspx?itemnum=735

Third Stage of Labor

• What is delivered during the third stage of labor?

• 5 to about 30 minutes

Methods of Delivery

• Vaginal

• Cesarean delivery

• Cesarean birth rates in U.S. are among highest in world

• When are cesarean births more likely to occur?

• Live birth: C-section surgery | Video | BabyCenter

Birth Complications

• Breech• Cross-wise position• Anoxia

– Position of baby– Cord is pinched, twisted– Placental abruption– Placenta previa

• Google Image Result for http://www.umm.edu/graphics/images/en/19159.jpg

Newborns at Risk

• Preterm

• Low birth weight

• Respiratory Distress Syndrome (RDS)

• Premature baby's first few minutes - NICU Team - YouTube

Medical and Behavioral Assessment

• Apgar Scale: 5 subtests, assessed 1 minute after and 5 minutes after delivery

• Newborn is rated 0, 1, or 2 on each measure:– A--– P--– G--– A--– R--

The Newborn Baby What is the neonatal period?

Newborn—neonate—about 20 inches long, 71/2 lbs.

Are boys or girls bigger?

Are first borns or later borns bigger?

Some features: Large head (1/4 the body length) Receding chin—why? Head may be misshapen—why? Why do babies have “soft spots” on their heads? What are they called? Pinkish cast—thin skin covering capillaries where blood flows What is the fuzzy prenatal hair that newborns have on their bodies called? What is the oily protection that babies are covered with when they are born? What

purpose does it serve?