PSYC 331 Ch 2: Birth and Prenatal Development

CH 2: Birth and Prenatal Development

-In the womb

-conception: joining of sperm and egg

-zygote: fertilized egg

-travels down the fallopian tube, implants in the uterine wall

-important processes of cells:

-division: cells divide and multiply rapidly

-form inner cell mass

-migration: cells in ICm change location, move around

-differentiation: location determines specialization

-death (apoptosis): unneeded cells are discarded

-time periods

-1-2 wks: germinal period (zygote, blastocyst)

-3-8 wks: embryonic period (embryo)

-9 wks-birth: fetal period (fetus)

-order in development

-cephalocaudal development: from “head to tail”

-proximodistal development: from “near to far” 

-timeline

-by 2 wks: blastocyst (zygote) implanted in uterine wall, cells differentiate

-4 wks: head and face develop, heart beats, circulates blood

-5.5-8 wks: facial features begin to form

-9 wks: eyes and ears begin to form, internal organs, fingers/toes are present, movements occur

-16 wks: lower body areas rapidly develop movement becomes pronounced, some reflexes are present, gender is observable

-18 wks: thumb sucking is observed

-20 wks: facial movements and expressions are present, fetus spends most of its time upside down

-28 wks: brain, lungs developed enough for birth, REM and brain waves are similar to newborn, auditory system is online

-fetus continues to develop for 38 wks or 266 days before finally being born

-fetus movement

-movement begins at 5-6 wks

-starts as jerky, uncoordinated, but improves with time, practice

-sleep-wake cycles become stable in the second half of pregnancy

-fetal perception

-sight: some light reaches the womb, but not much

-touch: infant moves and touches things in its environment 

-smell/taste: occurs through amniotic fluid

-hearing; infants can hear sounds from outside the womb and respond to them

-fetal cognition

-habituation: the fetus responds to sounds and habituates over time

-new born infants show preferences for familiar sounds from inside the womb

-their mother’s voice

-their own language

-the Cat in the Hat

-DeCasper & Spence, 1986

-tested newborns’ preference for familiar passages 

-mothers read stories to fetuses prior to birth 

-testing: passages made contingent on sucking rate

-results: infants sucked at the rate needed to hear the familiar passage

-tells us: infants hear, recognize and prefer familiar passages of birth

-Teratogens

-environmental agents that can harm the embryo or fetus

-critical (sensitive) periods: 

-different organs are vulnerable at different times

-harm can depend on when a teratogen is encountered

-common teratogens: 

-STD’s, drugs, environmental hazards, parental age, diseases

-STD’s

-HIV / AIDS: ¼ of infants born to infected mothers are infected themselves. Transmission can also occur through breast milk. 

-drugs

-thalidomide: drug taken to reduce pregnancy symptoms in the 1960s and can cause severe defects such as missing or stunned limbs if taken during the 2nd month of pregnancy

-heroin: lead to addiction in both mother and infant, low birth-weight, prematurity, stillbirth, and developmental delays

-marijuana; slower growth, low birth weight, and immature nervous system. May cause learning and memory impairments

-alcohol: fetal alcohol syndrome results indistinctive physical and cognitive defects including distractibility, poor-judgment, difficulty reading social cues 

-smoking: decreases the amount of oxygen available to the fetus, which can lead to impaired motor development, learning disabilities, mental retardation

-environmental hazards

-radiation, x-rays: can cause damage to eyes or CNS. Radiation from WW2 caused mental retardation and physical deformities in exposed children. 

-pollution: ???

-mercury: “minamata disease”

-lead

-parental age

-older women: women who give birth after their mid-thirties have increased risk of Down Syndrome, stillbirth and preterm babies

-older men: older sperm are more likely to be abnormal. Greater paternal age can increase likelihood of learning disabilities and mental disorders

-diseases

-rubella: viral infection that can lead to deafness, mental retardation, heart disease or blindness if contracted during the first 20 wks of pregnancy

-zika: microcephaly

-Birth

-the birth process

-after approximately 38 wks (266 days)

-signaled by regular uterine contractions

-4-5 mins apart

-dilation of cervix, widening about 10 cm

-baby becomes visible in birth canal, is pushed out

-finally placenta follows

-head plates are not fused, allowing skull to flex

-allows for longer development in utero

-Newborns

-spend most of their time: 

-eating, sleeping, crying

-sleeping

-newborns spend ⅔ time sleeping

-half is active (REM) sleep

-bouts of sleep are short

-US infants don’t sleep through the night until about 4 months

-crying

-form of communication and help-seeking

-cause can be difficult to ascertain

-often peaks in late-afternoon/evening

-reflects: hunger, pain, discomfort, overstimulation