Transcript 2007 The McGraw-Hill Companies, Inc. All rights reserved.

Slide 1
4
Prenatal
Development
John W. Santrock
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
Slide 2
Prenatal Development
• What Is the Course of Prenatal Development?
• What Are Expectant Parents’ Experiences Like
During Prenatal Development?
• What Are Some Potential Hazards to Prenatal
Development?
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
What Is the Course of Prenatal Development?
Slide 3
The Germinal Period
• First two weeks after conception
– Creation of zygote
– Continued cell division
– Attachment of zygote to uterine wall
– Differentiation of cells has begun
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
What Is the Course of Prenatal Development?
Slide 4
Parts of the Zygote
• Blastocyst: inner layer of cells that
develops during the germinal period
– Later develops into embryo
• Trophoblast: outer layer of cells that
develops during germinal period
– Provides embryo nutrition and support
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
What Is the Course of Prenatal Development?
Slide 5
The Embryonic Period
• Two to eight weeks after conception
– Rate of cell differentiation intensifies
– Support systems for cells form
– Organogenesis: organ formation
– Embryo has three layers of cells
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
What Is the Course of Prenatal Development?
Slide 6
Parts of the Embryo
• Endoderm: inner layer of cells forming
digestive and respiratory systems
• Ectoderm: outermost layer of cells
forming nervous system, sensory
receptors, and skin parts
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
What Is the Course of Prenatal Development?
Slide 7
Parts of the Embryo
• Mesoderm: middle layer of cells
forming circulatory system,
bones, muscles, excretory and
reproductive systems
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
What Is the Course of Prenatal Development?
Slide 8
Embryo’s
Life-Support System
• Placenta: intertwines but does
not join mother and baby
• Umbilical cord: connects baby
to placenta
• Amnion and amniotic fluid:
provides baby’s environment
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
What Is the Course of Prenatal Development?
Slide 9
The Placenta and the Umbilical
Cord
Uterus
Umbilical
cord
Placenta
Fig. 4.1
Umbilical
vein
Umbilical
arteries
Fetal portion
of placenta
Maternal portion
of placenta
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
What Is the Course of Prenatal Development?
Slide 10
The Fetal Period
• Begins two months after conception;
lasts about seven months, until birth
• Largest prenatal size and weight gains
• Fingers, toes, skin, features, lungs,
other structures, and reflexes all
develop to prepare for birth
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
What Is the Course of Prenatal Development?
Slide 11
The Fetal Period
• The three trimesters are not same
as the three prenatal periods
• At birth, average baby weighs 7.5
pounds and is about 20 inches
long
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
Third
trimester
begins
About 16.518 inches
long, weighs
4 to 5 pounds
32 weeks
About 14-17
inches long,
weighs 2.5
to 3 pounds
19 inches
long, weighs
6 pounds
Less than
1/10th of an
inch long
About 11-14
inches long,
weighs 1 to
1.5 pounds
About 10-12
inches long,
weighs 1/2
to 1 pound
First
trimester
begins
Slide 12
The three
trimesters
of prenatal
development
Less than
1 inch long
About 5.5
inches long,
weighs about
4 ounces
About 3
inches long,
weighs about
1 ounce
Second trimester
begins
© 2007 The McGraw-Hill
Companies, Inc.
All rights reserved.
What Are Expectant Parents’ Experiences Like During Prenatal Development?
Slide 13
Confirming the Pregnancy and
Calculating the Due Date
• Pregnancy test checks for human
chorionic gonadotropin (HCG)
• Pregnancy calculated from first day
of the woman’s last menstrual period
– Lasts about 280 days or 40 weeks
• Fetal life begins at ovum fertilization
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
What Are Expectant Parents’ Experiences Like During Prenatal Development?
Slide 14
Early Signs and Symptoms
of Pregnancy
Fig. 4.4
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
What Are Expectant Parents’ Experiences Like During Prenatal Development?
Slide 15
Three Trimesters and
Preparation for Birth
First trimester
Very tired; nausea and
pregnancy sickness; breasts
change; emotional changes
Second trimester
Less fatigue and nausea; uterus
expands into abdominal cavity
Third trimester
Anticipates end; uterus expands
to point below breastbone
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
What Are Expectant Parents’ Experiences Like During Prenatal Development?
Slide 16
Preparation for the Baby’s
Birth
• Braxton Hicks contractions increase
• Cervix becomes softer and thinner
• Awkwardness
• Fatigue and desire for pregnancy to end
• Nesting urge and spurts of energy
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
What Are Expectant Parents’ Experiences Like During Prenatal Development?
Slide 17
Expectant Mother’s
Nutrition and Weight Gain
• Nutrition
– Need for protein, iron, vitamin D,
calcium, phosphorus, magnesium
increases 50 percent, water is
essential
• Weight Gain
– 25 to 35 pounds associated with
best reproductive outcomes
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
What Are Expectant Parents’ Experiences Like During Prenatal Development?
Slide 18
Expectant Mother’s
Nutrition and Weight Gain
• Weight Gain
– Maternal obesity adversely impacts
pregnancy outcomes; carries risks
• Hypertension
• Diabetes
• Respiratory complications
• Infections
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
What Are Expectant Parents’ Experiences Like During Prenatal Development?
Slide 19
Exercise During Pregnancy
• Exercise for shorter
time intervals
• Decrease intensity as
pregnancy progresses
• Avoid prolonged
overheating
• Avoid high-risk
activities
• Warm up, stretch, cool
down
• After exercise, lie on
left side 10 minutes
• Wear supportive shoes
and bra
• Reduce exercise
significantly in the last
four weeks
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
What Are Some Potential Hazards to Prenatal Development?
Slide 20
Some General Principles
• Teratogen
– Any agent that causes a birth defect
– Only about half of potential effects appear
at birth
• Severity and type of defect affected by
– Dose
– Genetic susceptibility
– Time of exposure
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
What Are Some Potential Hazards to Prenatal Development?
Slide 21
Prescription and
Nonprescription Drugs
•Damage discovered after a cluster
of deformed babies is born
– Specific antibiotics
– Some antidepressants
– Certain hormones
– Diet pills
– Aspirin
– Caffeine
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
Terogens and Timing of Their Effects on
Prenatal Development
Slide 22
Zygote
1 2
Embryonic period (wks)
Fetal Period (wks)
3
4
5
6 7 8 9 16 32 38
Central nervous system
Most
Heart
serious
Arms
damage
Eyes
from
teratogens
Legs
in first 2–8
Ears
weeks
Teeth
Period of susceptibility
Palate
to structural defects
External genitalia
Period of susceptibility
to functional defects
Fig. 4.7 (modified)
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
What Are Some Potential Hazards to Prenatal Development?
Slide 23
Psychoactive Drugs
• Psychoactive drugs
– Act on nervous system
– Alter states of conscious
– Modify perceptions
– Change moods
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
What Are Some Potential Hazards to Prenatal Development?
Slide 24
Psychoactive Drugs
• Alcohol
– Fetal alcohol syndrome (FAS)
•
•
•
•
•
Nicotine
Cocaine
Marijuana
Methamphetamine
Heroin
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
What Are Some Potential Hazards to Prenatal Development?
Slide 25
Environmental Hazards
• Fathers’ exposure to lead and
radiation
• Certain pesticides
• Petrochemicals
• Environmental pollutants and toxins
• Toxic waste
• Manufactured chemicals
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
What Are Some Potential Hazards to Prenatal Development?
Slide 26
Infectious Diseases
• Rubella
• Sexually transmitted infections
– Syphilis
– Genital herpes
– AIDS, HIV infection
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
What Are Some Potential Hazards to Prenatal Development?
Slide 27
Incompatible Blood Types
• Between mother and father
• Between mother and baby
– Blood group (A, B, O, AB)
– Rh factor (positive, negative)
– Vaccine within 3 days of birth
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
What Are Some Potential Hazards to Prenatal Development?
Slide 28
Other Parental Factors
• Maternal nutrition and low birthweight
• Obesity during pregnancy
• Maternal age—too young, too old
• Paternal age and risks
• Emotional states and stress
• Maternal hormonal treatments
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.