Prenatal and Infant Development
Mr. Koch
AP Psychology
Forest Lake High School
Conception
• A single sperm fertilizes a
single ovum (egg) to create
a zygote
– “germinal stage” - process of
rapid cell division and then
differentiation
– At about 10 days, attaches to
wall of uterus
• Outer cells form placenta, inner
cells develop into embryo
Embryonic Stage
• Stage from 2-9 wks after
conception
– Organs begin to form and
function
• Develops heart, nervous system,
stomach, esophagus, ovaries or
testes
• Develop eyes, ears, nose, jaw,
mouth lips
• By end have tiny arms w/ elbows,
hands, fingers
• Legs have knees, ankles, toes
Fetal Stage
• 7 month period of prenatal
development, spanning 9 weeks from
conception to birth
– Begins to look distinctly human
– Organs grow and start to function
• By 3 months: can kick, make fist, turn
head, open mouth, swallow, frown
• In 6th month: eyelids open, has
tastebuds, well-developed grasp, can
breathe regularly as long as 24 hrs. at a
time
– Could potentially survive premature birth
by end of 6th month
• Organ systems typically functional by end
of 7th month
• 8th & 9th month: respond to light & touch,
hear outside sounds
– Can also learn – respond differently to
sound of mother (faster heartbeat) and
stranger (slower heartbeat)
Teratogens
• Potentially harmful agents (i.e. viruses,
chemicals) that can affect prenatal
development
• Placenta screens out most harmful substances, but
these sneak through
– Especially harmful if during embryonic stage
• “critical period” in prenatal development
– If heart, eyes, ears, hands, feet don’t appear, cannot form
later – if formed incorrectly, defects are permanent
– Teratogens during fetal stage affect size, behavior,
intelligence, and health
Teratogens
• Disease
• Can be born with AIDS or experience physical
defects from other diseases like rubella
• Drugs (i.e. heroine, cocaine, crack)
• Can be born addicted
• “Crack babies”
– premature, underweight, tense, fussy, delayed
physical growth & motor development, behavior
& learning problems
• Smoking/nicotine
• Can cause respiratory problems, irritability,
social/attention problems, greater risk for
nicotine addiction later in life, can harm brain
development
• Can cause reduction of nutrients that can lead
to premature and underweight birth, which
can cause cognitive and behavioral problems
Teratogens
• Alcohol
• Can kill fetal brain cells – depresses
fetal nervous system, putting at risk
for birth defects & mental retardation
– Fetal Alcohol Syndrome (FAS)
• Characterized by mental retardation,
possible physical malformations
• Behavioral and psychological problems
also linked to mothers experiencing
significant stress, depression, or flu in
first 6 months
• Fortunately, vast majority of infants
(>90% in western nations) are born
without mental or physical problems
Newborns
• How do we study capabilities of infants?
– Very difficult – present stimuli & monitor response
– Eye movements, changes in heart rates, sucking rates, brain
waves, body movements, and skin conductance
• Can see at birth
– Blurry, but able to see large, close objects
» Seem to prefer faces and seem prepared to distinguish
from other visual stimuli
• Born with limited hearing capabilities
– Notice single note differences of tone, turn head toward
sounds, particularly attuned to sounds of speech
• Similar sense of smell & taste to adults, but less
developed
– Breast-fed infants show preference for smell of own mother
to others
• In general, infants’ sensory abilities seem to dispose to
focus attention on caregiver
Newborns
• Born with numerous reflexes
that aid survival
– Involuntary, unlearned motor
behaviors
– Ex. “rooting” reflex, sucking, etc.
• Most disappear in 3-4 months
when brain development allows
voluntary control of muscles and
development of motor skills
Newborns
• Brain development
• Born with overabundance of neurons, but immature
(connections poorly developed)
• After birth, neural networks develop rapidly until
puberty when “pruning” process gains importance
Newborns
• Brain development helps enable maturation
– Natural growth or change that unfolds in a fixed
sequence, relatively independent of environment
– Must be biologically prepared for certain changes
to develop
• Age of maturation will vary, but sequence rarely does
• However, research shows that once properly matured,
experience can impact efficiency, effectiveness of
development
– Once again, nature and nurture interact