PSYC302 (Infancy) Module 3 & 4 Notes

PSYC302 – Infancy Lecture Notes
Module 3 - Prenatal Development, Birth, and the Newborn Baby
Lesson 6: Prenatal Development
Conception
- Sperm and ovum unite
- Ovum is released from ovaries every 28 days
 survives for one day
- Sperm live in fallopian tube for up to six days
- Most conceptions result from intercourse on
day of ovulation or during two days
preceding it

Milestones of Prenatal Development
1. Germinal (0-2 weeks)
 Weeks 1 – 2
 Fertilization and formation of the
zygote
 Implantation of the blastocyst
 Development of nourishing and protective structures:
o Amnion: membrane forming a fluid-filled cavity (amniotic sac) that
encloses the embryo, protecting the developing baby from the mother's
body and provides nutrients, immune protection, waste removal, and
gas exchange for the growing baby.
o Chorion: membrane that surrounds a developing fetus in conjunction
with the amnion, plays a key role in the exchange of blood and gases
between mother and fetus and develops into the fetal aspect of the
placenta.
o Yolk sac: structure that develops inside uterus, provides embryo with
nourishment (food), circulates gasses between mother and embryo,
produces cells that turn into important structures, like umbilical cord,
blood cells and reproductive organs.
o Placenta: temporary organ that develops during pregnancy, attaches to
the lining of uterus and delivers oxygen and nutrients to growing baby
through umbilical cord.
o Umbilical cord: tube that connects mother to baby during pregnancy 
three blood vessels: one vein carries food/oxygen from placenta to baby
and two arteries carry waste from baby back to placenta.
2. Embryonic (3-8 weeks)
 Forebrain, midbrain, hindbrain formed
 Central nervous system, internal organs, muscles, skeleton begin to form
o Heart begins pumping blood
o Neurons develop rapidly
 External features form: eyes, ears, nose, limbs
3. Fetal (9 weeks-birth)
 First trimester:
o Organs, muscles, and nervous system organize
o Lungs begin to expand and contract
o Sex of fetus detectable with ultrasound
 Second trimester:
o Fetus is active; mother can feel movement

, o Neurons rapidly form synapses
o Sensitivity to sound and light emerges
 Third trimester:
o Age of viability: 22 – 26 weeks
o Substantial growth and weight gain
o Rapid gains in neural connectivity and organization
o Expanding sensory and behavioural capacities, signs of developing
temperament

Placenta and Umbilical Cord
- At the end of the germinal period and the beginning of the embryonic period, the
placenta develops
- The umbilical cord connects the fetus to the placenta
 Permits transfer of food and oxygen
 Takes waste products away
- A membrane separates the mother’s blood from the embryo’s blood

Prenatal Environmental Influences
Teratogens
- Environmental agents that cause damage during the prenatal period
- Effects depend on:
 Dose  “the dose make the poison”
 Heredity
 Presence of other negative factors
 Age and prenatal sensitive periods

Teratogenic Substances
- Drugs
 Prescription and Non-prescription
o Isotretinoin (acne treatment)
o Aspirin
o Caffeine
o Antidepressants
 Illegal
o Cocaine
o Heroin
- Tobacco
 10% of the US women smoke while pregnant
 Low birth weight is more known effect
 Increase risks of miscarriage, prematurity, abnormalities, heart rate and
breathing problems, infant death, later asthma and cancer, and long-term
cognitive and behaviour problems
 Passive exposure also increases risk
- Alcohol
- Radiation and environmental pollution
 Radiation
o Even low-level exposure is harmful
o Examples: industrial leakage, medical X-rays
 Environmental pollution

, o Many babies are “born polluted”
o Examples: mercury, PCBs, dioxins, lead, traffic-related fumes
 Can cause variety of physical defects and cognition impairments  increases
chances of later illnesses
- Infectious diseases
 Rubella
 HIV/AIDS
 Herpes
 Toxoplasmosis

The Thalidomide Crisis
- Early 1960s
- Canada widely prescribed a sedative drug, thalidomide, to reduce morning sickness
- It was later found to cause severe deformities
- About 7,000 infants worldwide were affected before it was removed from the market

Cannabis
- Use is increasing in Canada due to legalization
- Linked with numerous development delays and difficulties
- Lasting consequences not well-established

Fetal Alcohol Spectrum Disorder
- Range of outcomes caused by prenatal alcohol exposure:
 Fetal alcohol syndrome (FAS)
 Partial fetal alcohol syndrome (p-FAS)
 Alcohol-related neurodevelopmental disorder (ARND)
- Consequences:
 Slow physical growth
 Facial abnormalities
 Mental impairment

Crucial Maternal Factors
- Nutrition
 Prenatal malnutrition can lead to damaged organs and CNS, increased
chances of illness and disease later in life
 Vitamin-mineral enrichment is crucial, e.g., folic acid supplementation 
reduces neural abnormalities and defects by 70%
- Emotional stress/distress
 Deprives fetus oxygen and nutrients
 Stress hormones cross the placenta causing dramatic rise in fetal stress
hormones
 Associated with negative behavioural outcomes in children and youths and
with susceptibility to later illness
 Social support reduces risk of complications
- Maternal age

Importance of Prenatal Care
- Can detect and treat complications
- Reduces likelihood of low birth weight and fetal death
- Culturally sensitive practices also helpful