Prenatal and Infant Development
Mr. KochAP 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