Chapter 4

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
Conception to 2 weeks
2-8 weeks
8 weeks to birth
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
When and where does fertilization take
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
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
• Skin
• Nerves
• Sense organs
• Muscle
• Bones
• Circulatory system
• Some organs
• 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,
• Size increases
• Cephalocaudal/
• Proximodistal Principles
• Finishing touches – toenails,
• Appearance of bone
• Fetal Development Pictures
Slideshow: Photos Month-byMonth by WebMD
Figure 3.3—Sensitive Periods in
Prenatal Development
Prenatal Development: Ultrasound Imaging
Chromosomal Abnormalities
• Typically occur because of
errors in cell division
• Result is extra or missing
• http://www.biology.iupui.e
Karyotype of Down Syndrome
Dominant/Recessive Inheritance
Every person inherits a pair of alleles for a
particular characteristic from each parent
What does it mean to be homozygous for
a trait?
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
• 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
Chorionic villi
False positives
False negatives
Stages of Childbirth
• First stage—usually the
longest—12 hours or
more, especially for first
• What happens during
the first stage of
Second Stage of Labor
Usually lasts up to one hour
What is happening with the
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
Third Stage of Labor
• What is delivered
during the third stage of
• 5 to about 30 minutes
Methods of Delivery
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 |
Birth Complications
• Breech
• Cross-wise position
• Anoxia
Position of baby
Cord is pinched, twisted
Placental abruption
Placenta previa
• Google Image Result for
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:
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?