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
Stage
Duration
Germinal
Conception to 2 weeks
Embyronic
2-8 weeks
Fetal
8 weeks to birth
• http://thevisualmd.com/videos/r
esult/from_conception_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
• Skin
• Nerves
• Sense organs
Ectoderm
Mesoderm
Endoderm
• 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,
connected
• Size increases
• Cephalocaudal/
• Proximodistal Principles
• Finishing touches – toenails,
eyelids
• Appearance of bone
• Fetal Development Pictures
Slideshow: Photos Month-byMonth by WebMD
Figure 3.3—Sensitive Periods in
Prenatal Development
Prenatal Development: Ultrasound Imaging
• http://www.youtube.co
m/watch?v=PN3e7nyEx
qc&feature=fvsr
• http://www.youtube.co
m/watch?v=PN3e7nyEx
qc
Chromosomal Abnormalities
• Typically occur because of
errors in cell division
• Result is extra or missing
chromosome
• http://www.biology.iupui.e
du/biocourses/N100/2k2hu
mancsomaldisorders.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/grap
hics/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?