1. PSYC 206
Lifespan Development
Aylin C. Küntay

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. 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 4 4

5. The Three Trimesters of Pregnancy
Pregnancy is divided into three trimesters:
The First Trimester (Weeks 1-12)
The Second Trimester (Weeks 13-27)
The Third Trimester (Weeks 28-42)

6. At the cellular level
Cell division: These cells initially are all the same, perfectly interchangeable in structure & function; can flexibly become neuron versus liver cell; they're embryonic stem cells.
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. Interestingly, much of cell differentiation seems to depend on where the cell ends up when migrating.
Cell death: The selective death of some cells. For example, fingers develop as the cells between the fingers die off.
First, let’s talk about the processes that are involved in prenatal development. These are processes that are occurring at the cellular level. One of the most amazing aspects of prenatal development is that the organism develops from a single cell, the fertilized egg to an organism with many different kinds of cells. This happens through four major processes at the cellular level. Cell division. The first order of business following fertilization is cell division. These cells initially are all the same, perfectly interchangeable in structure & function; can flexibly become neuron versus liver cell; they're embryonic stem cells. Following division cells begin to migrate to different locations. Once cells move to different locations they begin to differentiate both in terms of structure & function. For example, some cell begin to form the placenta other become the neural tube forming the basis of the brain & the spinal cord. Interestingly, much of cell differentiation seems to depend on where the cell ends up when migrating. The final process is cell death. The selective death of some cells is important for normal development. The book shows an illustration of conseq. of cell death. For example, fingers develop as the cells between the fingers die off. These are the 4 proces that are responsib for the dev changes we observe from conception to birth. One of the critical things to notice in this process is that it is a continuous process and it emphasizes what happens at the cellular level. Now let’s take a look at video and see what it looks like. Watch the clip for 2 things. When do the changes look continuous and when do the changes look discontinuous implying s. qualitative transitions; Watch the clip for the things you need to pay attention to in chp 2 & 3 of the book for the details of neural development. 6

7. 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: From a single cell to hundreds of cells 7

8. 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 8

9. Embryonic Period Begins at implantation Lasts until the 8th week
Cell differentiation: all major organs have taken shape.
Organogenesis
Placenta
Acts as a barrier that prevents the bloodstreams coming into direct contact
Acts as a filter that allows oxygen and nutrients be exchanged 9

11. Embryonic Period
Cell differentiation: all major organs have taken shape.
Organogenesis
Placenta
Acts as a barrier that prevents the bloodstreams coming into direct contact
Acts as a filter that allows oxygen and nutrients be exchanged 11 11

12. Placenta
The placenta communicates with the developing human through the vessels of the umbilical cord. 12

13. Placenta
delivers maternal oxygen, nutrients, hormones, and medications to the developing human
removes all waste products
prevents maternal blood from mixing with the blood of the embryo and fetus
maintains embryonic and fetal body temperature slightly above that of the mother's. 13

14. Placenta Source of Nutrition
As the mother eats, the food passes through the digestive system where the body breaks it down into small particles the body can absorb. The nutrients travel through the mother's bloodstream and exchange to the bloodstream of the fetus through the placenta. In addition to ingested food, the mother's body continually breaks down muscle, fat and bones, releasing proteins, fat and calcium to the mother's blood that can be absorbed through the placenta to provide nutrients to the fetus. 14

17. 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). 17

18. From the Third through the Eighth Week
What happens during the embryonic period of prenatal development?
As nerves and muscles form links to the brain, the embryo now moves spontaneously, as the brain begins to move muscles.
The intestines begin to move from the umbilical cord to the embryo’s body cavity.
Brain
Intestines
Eyes and eyelids are developed. Eyes will continue to migrate to the front of the head, where they will eventually rest. Eyelids begin to grow together and are only half closed. External, middle, and inner ears are now fully formed. External ears will continue to migrate to the side of the head, where they will eventually rest.
Arms are well formed, longer, and can bend at elbows and move forward. Fingers elongate and digits are fully separated. Each finger has three digits, and the thumb has two digits.
Arms, hands and fingers
Facial Features
Urogenital membranes have developed into either male or female organs, and ovaries or testicles are visible. Clitoris or penis begins to form, but distinguishing the embryo’s sex is difficult.
External sex organs
Brain
Facial Features
The head is still disproportionately large but is erect and appears rounded. The neck is well defined. The tail will disappear by the end of this week. Cartilage begins to turn into bone. The ectoderm layer is replaced by the beginnings of skin. The body becomes evenly rounded, due to the growth in the abdomen.
Arms, hands and fingers
Intestines
Overall appearance
External sex organs
Overall appearance 18

19. 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. 19

20. Fetal Period
Movement promotes coordination and refinement of the nervous system
Basic sensory capacities developing
Example: sensing motion, light, sound 20

21. 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

22. 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”.
Conclusion: learning: habituation decrease in response to a repeated stimulus
Babi-Biba 22 22

23. Fetal Learning
Sounds presented: Babi-Biba

24. Fetal Period
In utero experience influences infant's preference for maternal voice. Sensory development in the prenatal period allows the baby to engage the environment socially at birth and before.
The tactile sense is the first to develop prenatally and the most refined sense at birth.
Auditory development is completed during the prenatal period. Auditory ability gives us the clearest picture of prenatal learning. Newborn babies show a marked preference for voices heard during the prenatal period.

25. Fetal Learning E.g.: work by DeCasper & Spence (86)
IV: “Cat in the Hat” vs. new story
mothers read “cat in the hat” everyday for the last 6 weeks of pregnancy
DV: sucking rate
A pacifier was wired to record sucking rates.
2 minutes: to establish a baseline rate
Changes in sucking rate turned on or off a tape recording of their mothers reading a story. 25

26. Fetal Period Fetal learning
Example: work by DeCasper and Spence (1986)
Conclusion: prefer the familiar
Babies recognized the story read to them twice a day in the last six weeks of pregnancy when compared to an unfamiliar story that was heard for the first time after birth. 26

27. 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 27

28. What happens during the fetal period of prenatal development?
From the Ninth Week until Birth
What happens during the fetal period of prenatal development?
9 weeks through 38 weeks 9 12 16 20 24 28 32 36 38
fetus: A developing human organism from the start of the ninth week after conception until birth. 28

29. 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
(f) 36 weeks (full term) 29

30. 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 30

31. 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 31

32. Sensitive periods for teratogens32

33. 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 33
Source: Adapted from K.L. Moore & Persaud. 2003

34. Maternal factors (nutrition)
Spina bifida ("split spine") is a developmental disorder caused by the incomplete closing of the embryonic neural tube. Some vertebrae overlying the spinal cord are not fully formed and remain unfused and open.
Executive function, attention, inhibitory control, academic skills, learning disabilities, discalculia
Spina bifida can be surgically closed after birth, but this does not restore normal function to the affected part of the spinal cord. Intrauterine surgery for spina bifida has also been performed, and the safety and efficacy of this procedure is currently being investigated.
The incidence of spina bifida can be decreased by up to 70% when daily folic acid supplements are taken prior to conception.

35. Teratogens
Dose-response relationship (length & amount of exposure determine degree of harm)
Effects are not uniform: significant individual differences in susceptibility
Many harmful agents cause major damage only if exposure occurs during a sensitive period
Sleeper effects 35 35

36. 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

37. 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. 37 37

38. 38

39. Teratogens: Environmental Sources of Birth Defects
Cerebral cortex size 39

40. 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.

41. Teratogens: How much alcohol?
FAS: equivalent of 3 shot glasses of whiskey
5 or more drinks on a single occasion
Lower levels of alcohol consumption: mixed evidence
No discernible harm
Measurable deficits in cognitive and motor functioning
A set of genes control the way we metabolize alcohol. If the mother has this set of genes and metabolize alcohol in a certain way, they are much more likely to have babies with FAS.

42. 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

43. Gene-environment interactions
There’s no safe amount!
Individual differences in susceptibility
Set of genes control the way each of us metabolize alcohol
The ingestion of alcohol does not always result in FAS, but no amount of alcohol whatsoever is proven safe for consumption during pregnancy. The current recommendation of both the Surgeon General of the United States and the British Department of Health is not to drink alcohol at all during pregnancy. 43

44. Environmental pollutants
Lead & Mercury
Occupational hazards (e.g. farmers pesticides; additive chemicals in factories)
pollutants affect CNS growth but they are also associated with sleeper effects.
Exposure to all three classes of pollutants are strongly associated with low SES.

45. 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 45

46. Maternal Factors Related to Child Health
Age
Nutrition
Disease
Stress

47. Conclusion Prenatal development not simply biologically pre-programmed
Environmental events and biology interact to determine developmental outcomes
INTERACTIONIST VIEW

48. 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 48

49. First Minutes and Complications
Apgar scale: A quick assessment of a newborn’s health, given twice (at one minute and five minutes after birth).
How is a
Newborn tested? 49

50. The Apgar Scale Assesses physical condition
Factors rated: Heart rate, respiratory effort, muscle tone, reflex responsivity, color
A low score requires immediate medical attention 50

51. 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 51

52. Problems and Complications
Prematurity
Birth before the 37th week
Immature lungs, digestive, or immune systems
Low Birth Weight
Below 2500 grams
Intrauterine growth restrictions 52

53. 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?” 53