1. PSYC 206
Lifespan Development
Bilge Yagmurlu

2. Chapter Overview The Periods of Prenatal Development
Environmental Conditions and Prenatal Development
Teratogens: Sources of Birth Defects 2

3. The Period of Prenatal Development
Divided into three broad periods:
Germinal Period
Embryonic Period
Fetal Period 3

4. At the cellular level
Cell division: These cells initially are all the same.
Cell migration & Cell differentiation: Following division cells begin to migrate to different locations. and begin to differentiate both in terms of structure & function. For example, some become the neural tube forming the basis of the brain & the spinal cord.
Cell death: The selective death of some cells.

5. Germinal Period Begins at conception Lasts until implantation
Implantation: process by which the organism becomes attached to the uterus
8 to 10 days after conception
Cell division 5

6. How does implantation occur?
The First 14 Days
implantation: The process beginning about 10 days after conception, in which the developing organism nestles in, and attaches to the placenta that lines the uterus.
How does implantation occur?
The Most Dangerous Journey
Conception
Zygote (single cell)
Two-celled stage
Fallopian tube
Ova
Sperm
Ovum
Implantation
Ovary 6 6

7. Embryonic Period Begins at implantation Lasts until the 8th week
Cell differentiation
Organogenesis
Placenta 7

8. 8

9. Placenta
The placenta communicates with the developing human through the vessels of the umbilical cord. 9 9

10. Placenta
When the fetus is born, its placenta begins a physiological separation for spontaneous expulsion afterwards (and for this reason is also called the afterbirth). 10 10

11. Fetal Period Begins at the 9th week Lasts until birth
Growth in weight and length
Brain and all organ systems increase in complexity
Existing structures are refined
By 15 weeks the fetus exhibits all movements observable at birth. 11

12. Fetal Period
Movement promotes coordination and refinement of the nervous system
Basic sensory capacities developing 12

13. Characterizing the fetus & its experience
Movement ~ 5wks
Sensory experience
Smell: Amniotic fluid has odor of what mom ate; During fetal breathing, amniotic fluid comes into contact with olfactory receptors
Hearing: Internally generated sounds (mom’s heartbeat, breathing, etc.); Externally generated sounds (mom’s voice and people talking to her); Fetus moves & shows heartbeat changes
Touch: Grasping, sucking, rubbing, bumping walls of uterus
Taste: Swallows amniotic fluid
Fetus has a sweet tooth
Sight: Negligible

14. Fetal Period Fetal learning
Example: Sandman et al. (1997) experimental study
Sample: 32 wk-old fetuses
DV: Heart Rate
IV: Old vs. new sounds. presented (via a loudspeaker near the mother’s abdomen) fetuses with a speech sound “babi”. 14

15. Fetal Period Fetal learning: Does learning survive birth?
Example: work by DeCasper and Spence (1986)
DV: sucking rate
IV: “Cat in the Hat” vs. new story
Conclusion: prefer the familiar 15

16. Stages of Prenatal Development
Germinal period
Zygote
Embryonic period
Embryo
Fetal period
Fetus
Implantation to
Organogenesis
+6 weeks
Organogenesis to
Birth
+30 weeks
Conception to
Implantation
2 weeks

18. Prenatal Brain Development
Brain stem
Hindbrain
Neural tube
(forms spinal cord)
Forebrain
(a) 25 days
Midbrain
Prenatal Growth of the Brain
How does the brain grow during the periods, or stages, of prenatal development?
(b) 50 days
(c) 100 days
(d) 20 weeks
(e) 28 weeks 18
(f) 36 weeks (full term) 18

19. Environmental Conditions and Prenatal Development
Maternal factors (age, nutrition, stress, disease, etc.)
Teratogens: Environmental agents that increase risk of deviation in normal development, can lead to abnormalities or death 19

20. Teratogens Common Teratogens: Effects can vary considerably Drugs
Including prescription drugs, caffeine, tobacco, alcohol, marijuana, cocaine, and heroin
Infections (including rubella and HIV)
Radiation or pollution at high levels
Effects can vary considerably 20

21. Teratogens Dose-response relationship
Effects are not uniform: significant individual differences in susceptibility
Many harmful agents cause damage only if exposure occurs during a sensitive period
Sleeper effects 21 21

22. Sensitive periods for teratogens

23. What are the risks at different stages of development?
Birth Defects from Teratogens: Time of Exposure and Effect on Major Organs
Germinal Period
Main Embryonic Period (in weeks)
Fetal Period (in weeks) 1 2 3 4 5 6 7 8 9 16 32 38
Common site(s)
of action of
teratogens
Highly critical
period
Less critical
period
Central nervous system
Neural-tube defects
Mental retardation
Learning disabilities
Heart
Arms
Legs
Lips
Cleft lip
Ears
Low-set malformed ears and deafness
Eyes
Cataract, glaucoma
Teeth
Enamel staining
Palate
Cleft palate
Sex organs
Masculinization of
female genitalia
Teratogens often
prevent implantation
Major congenital anomalies
Functional defects and minor anomalies 23 23
Source: Adapted from K.L. Moore & Persaud. 2003

24. Teratogens Fetal Alcohol Syndrome (FAS)
A set of symptoms that includes an abnormally small head and underdeveloped brain, eye abnormalities, congenital heart disease, joint anomalies, and malformations of the face 24

25. Teratogens: immediate vs. sleeper effects
Alcohol
Fetal alcohol syndrome
(FAS)
Low IQ
Poor attention
Hyperactivity
Slow physical growth
If no FAS
Attention-deficit hyperactivity problems
Cigarettes
Low birth weight
Less attentive to sounds
Lower IQ
Cancer
Illegal Drugs
Prematurity
Low birth weight
Physical defects
Breathing problems
Addicted at birth
Difficult to care for

26. Gene-environment interactions
Individual differences in susceptibility

27. Teratogens: Environmental Sources of Birth Defects
Cranio-facial abnormality
Cerebral cortex size

28. Alcohol crosses the placental barrier and can stunt fetal growth or weight, create distinctive facial stigmata, damage neurons and brain structures, and cause other physical, mental, or behavioral problems.
The main effect of FAS is permanent CNS damage, especially to the brain. Developing brain cells and structures are underdeveloped or malformed by prenatal alcohol exposure, often creating an array of primary cognitive and functional disabilities (including poor memory, attention deficits, impulsive behavior, and poor cause-effect reasoning) as well as secondary disabilities (e.g., mental health problems, and drug addiction).
The risk of brain damage exists during each trimester, since the fetal brain develops throughout the entire pregnancy.

29. Individual differences in susceptibility
Romitti et al., 1999
DV: Oral cleft defects
Predictors:
Child’s genes
Mother’s smoking & alcohol consumption
Incidence 1 in 1000 live births
Smoking-alcohol increases incidence at least 2-3 fold
Genetic markers and smoking-alcohol increases incidence 3-6 fold

30. Teratogens Six general principles apply to all teratogens:
The susceptibility of the organism depends on its developmental stage.
A teratogen’s effects are likely to be specific to a particular organ.
Individuals vary in their susceptibility to teratogens.
The mother’s physiological state influences susceptibility.
The greater the concentration of a teratogenic agent, the greater the risk.
Teratogens that have little or no effect on the mother can seriously affect the developing organism

31. The Newborn’s Condition
Assessing the Baby’s Vitality
The Apgar Scale
Physical condition
Brazelton Neonatal Assessment Scale
Behavioral condition
Primary Goal:
Screen for infants at risk
Secondary Goal:
Predict aspects of future development 31

32. Physical Condition The Apgar Scale Assesses physical condition
Factors rated:
Heart rate
Respiratory effort
Muscle tone
Reflex responsivity
Color
A low score requires immediate medical attention 32

33. 33

34. Behavioral Condition Brazelton Neonatal Assessment Scale
Assesses subtle aspects behavior
Includes tests of:
Reflexes
Motor capacities
Muscle tone
Responsiveness to objects and people
Control of own behavior 34

35. Problems and Complications
Prematurity
Birth before the 37th week
Immature lungs, digestive, or immune systems
Low Birth Weight
Below 2500 grams
Intrauterine growth restrictions 35 35

36. Closing Thoughts
From what you discovered about prenatal development in these slides, what examples can you cite to support the statement, “The most dramatic and extensive transformation of the entire life span occurs before birth?” 36