1. Chapter 4: Prenatal Development and Birth
McGraw-Hill
© 2006 by The McGraw-Hill Companies, Inc. All rights reserved.

2. Prenatal Development

3. Prenatal development is divided into 3 periods and lasts approximately 266 days
Germinal period: first 2 weeks after conception, zygote created (see Fig. 4.1)
Embryonic period: occurs from 2 to 8 weeks after conception (see Fig. 4.2)
Fetal period: begins 2 months after conception and lasts until birth

4. The Three Trimesters of Prenatal Development
Conception to 4 wks
To 8 weeks
To 12 weeks
To 16 weeks
To 20 wks
To 24 wks
To 28 wks
To 32 wks
36 to 38 weeks
Less than 1/10th of an inch long
Less than 1 inch long
About 16.5–18 inches long, weighs 4 to 5 pounds
19 inches long, weighs 6 pounds
About 5.5 inches long, weighs about 4 ounces
About inches long, weighs 1/2 to 1 pound
About inches long, weighs 1 to pounds
About inches long, weighs to 3 pounds
About 3 inches long, weighs about 1 ounce
First trimester begins
Third trimester begins
The Three Trimesters of Prenatal Development
See Figure 4.3 in textbook for more details
Fig. 4.3
Second trimester begins

5. Teratogen: any agent that causes birth defects
Drugs (prescription, nonprescription)
Alcohol, tobacco
Environmental pollutants
Infectious diseases
Nutritional deficiencies
Maternal stress
Advanced age of a parent
Severity of damage to the unborn depends on
Dose
Time of exposure
Genetic susceptibility

6. Teratogens and Timing of Their Effects on Prenatal Development
Zygote Embryonic period (wks) Fetal Period (wks) 1 2 3 4 5 6 7 8 9 16 32 38
Central nervous system
Most serious damage from teratogens in first wks
Heart
Arms
Eyes
Legs
Ears
Teeth
Palate
Period of susceptibility to structural defects
External genitalia
Period of susceptibility to functional defects
Fig. 4.4

7. Fetal alcohol syndrome: abnormalities in newborn due to mother’s heavy use of alcohol in pregnancy
Abnormalities include:
Facial deformities
Defective limbs, face, heart
Most are below-average intelligence
Some are mentally retarded

8. Moderate drinkers during pregnancy had babies who were less attentive and alert even at 4 years of age
Maternal smoking can cause
respiratory problems
SIDS
ADHD
low birth weight

9. Illegal drugs that harm during pregnancy:
Cocaine
Marijuana
Heroin
Incompatible blood types (Rh factor)
Environmental hazards: exposure to radiation or chemicals
STDs, HIV infection, AIDS
Other maternal and paternal factors

10. Percentage of U.S. Women Using Timely Prenatal Care: 1990 to 2001
100
1990 90
2001 80 70 60 50
Percentage 40 30 20 10
Non-Latino White women
African American women
Latino women
Fig. 4.6

11. Birth

12. Three stages of birth:
Uterine contractions begin at 15 to 20 minutes apart and last 1 minute; this stage lasts an average of 12 to 24 hours
Baby’s head begins to move through dilated cervix opening; this stage lasts 1.5 hour on average
Afterbirth: umbilical cord, placenta, and other membranes are detached and expelled

13. Birth complications include anoxia:
insufficient oxygen to brain when delivery lasts too long
Birth and delivery methods:
Hospital delivery room
Home delivery with midwife
Lamaze method
Comparing birthweights in the United States and other countries

14. Low Birthweight Rates by Country Percentage of low-birthweight infants
Luxemburg
Low Birthweight Rates by Country
Sweden
Canada
China
Czech Republic
Switzerland
Italy
Cuba
Kazakstan
United Kingdom
United States
Mexico
Ethiopia
Nicaragua
Turkey
Philippines
Nepal
Pakistan
Sierra Leone
Haiti
Bangladesh 5 10 15 20 25 30
Percentage of low-birthweight infants
Fig. 4.7

15. Causes of low birthweight:
Preterm babies
Small-for-date babies
Problems in developing countries
Possible consequences of low birthweight:
Brain injuries
Lung and liver diseases
Learning disabilities
ADHD
Lower levels in reading and math achievement
Deficits are evident in adulthood

16. Full-term normal weight
Comparison of Overall Cognitive Processing Skills of Middle School Students Who Were Born with Low Birthweight or Normal Birthweight 20 30 40 50 60 70 80 90
100 10
Overall cognitive skills score
<750 g
750-1,499 g
Full-term normal weight
Fig. 4.8

17. About 50% of low-birthweight children are enrolled in special education programs
Low birthweight is linked to asthma
Some defects can be improved with
Early speech therapy
Intensive enrichment programs
Kangaroo care and massage therapy

18. Weight Gain Comparison of Premature Infants Who Were Massaged with Those Not Massaged
3 lb. 7 oz
3 lb. 5 oz
Premature infants who were not massaged
3 lb. 3 oz
3 lb. 1 oz
Infant weight
2 lb. 15 oz 2 4 6 8 10 12 14
Age (days)
Fig. 4.9

19. Measuring neonatal health and responsiveness:
Apgar Scale, used 1–5 minutes after birth:
evaluate heart rate, body color, muscle tone, respiratory effort, and reflex irritability
Brazelton Neonatal Behavioral Assessment Scale performed within 24–36 hours after birth
27 items are organized into 4 categories – physiological, motoric, state, and interaction
Assesses newborn’s neurological development, reflexes, and reactions to people

20. The Apgar Scale 1 2 Score Body Color Blue, pale1 2
Body Color
Blue, pale
Body pink, extremities blue
Entire body pink
Heartbeat
Absent
Slow – less than 100 beats per min.
Fast – 100 to 140 beats per min.
Reflex Irritability
No response
Grimace
Coughing, sneezing, crying
Muscle Tone
Limp and flaccid
Inactive, weak, some flexion of extremities
Strong, active motion
Respiratory Effort
Breathing for no more than 1 min.
Irregular and slow
Breathing good with normal crying
Fig. 4.10

21. The
Postpartum
Period

22. Postpartum period lasts about 6 weeks after childbirth when woman adjusts physically and psychologically back to the prepregnant state
Influenced by preceding conditions and experiences
Mother learns to care for the baby, feel good about herself and those close to her
Physical: hormone changes, weight loss, return to menstruation, loss of energy or fatigue
Psychological: feelings of depression, anxiety, coping in new role, excessive worrying

23. Percentage of U.S. Women Who Experience Postpartum Blues and Postpartum Depression
Postpartum blues: symptoms appear 2 to 3 days after delivery and subside within 2 to 3 weeks
10%
70%
20%
No symptoms
Postpartum depression: symptoms linger for weeks or months and interfere with daily functioning
Fig. 4.11

24. Bonding (formation of emotional attachment) between infant and mother:
Usually occurs in period shortly after birth
Critical component in child’s development
Isolation of premature baby and use of drugs in birth process may harm bonding process
Some experts advocate a rooming-in arrangement while mother and child are in the hospital

25. The End