Lifespan overheads, chapter 3: prenatal development, birth, and the newborn
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prenatal development, birth, and the newborn baby
Conception:
 Most conceptions happen from intercourse during a 3 day
period: on the day of ovulation or in the 2 days prior.
Prenatal development:
 the period of the zygote (2 weeks)
 Implantation: zygote gets attached to the wall of the uterus (7th
to 9th day)
o blastocyst within 4 days of conception
 inner layer is embryonic disk.
 outer layer will develop into the amnion
o Only about 70% of zygotes get successfully implanted.
o By the end of the 2nd week, the chorion surrounds the
amnion
o Villi form the chorion burrow into the uterine wall, creating
the start of the placenta.
o placenta will permit food and oxygen to reach the
developing organism and waste products to be carried
away.
o umbilical cord contains one vein that delivers blood with
nutrients, and two arteries that remove waste products.
 period of the embryo: (2nd week to 8th week)
 embryonic disk forms 3 layers of cells:
1) ectoderm (nervous system, and skin)
2) mesoderm (muscles, skeleton, circulatory system,
internal organs)
3) endoderm (digestive system, lungs, urinary tract,
glands)
 The second month: eyes, ears, nose, jaw, and neck form.
o buds become arms, legs, fingers, toes.
o heart develops separate chambers
o liver and spleen start to produce blood cells.
o about 1 inch long, it responds to touch, can move
Lifespan overheads, chapter 3: prenatal development, birth, and the newborn
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 Period of the fetus: (9th week to birth)
 3rd month: fetus can kick, bend its arms, form a fist, curl its toes,
open its mouth, suck its thumb
o the lungs start to expand and contract in rehearsal of
breathing
o by the 12th week, the external genitals are formed
o heartbeat can be heard through a stethoscope
o at the end of the 3rd month, the 1st trimester is complete
 2nd trimester:
o vernix covers the skin, lanugo covers the body
o at the end of this trimester, most brain neurons are in
place
o stimulated by sound and light
 3rd trimester:
o age of viability: some time between 22 and 26 weeks
o the cerebral cortex enlarges, fetus spends more time
awake
o around 24 weeks fetuses can feel pain
o by 25 weeks, react to sounds with body movements
o in the last week of pregnancy they learn to prefer their
mother’s voices
o gains more than 5 lbs and grows 7 inches in this trimester
o in 8th month, a layer of fat is laid down
o gets antibodies from mom
Prenatal Environmental Influences
 teratogens:
 effects on a structure worst when that structure is being formed
 not all embryos or fetuses are equally affected
 the same defect can be caused by different teratogens
 a single teratogen can result in several different kinds of defects
 longer exposure/higher dose increased likelihood of serious
harm
 most of the organs and body parts develop in the period of the
embryo
Lifespan overheads, chapter 3: prenatal development, birth, and the newborn
Harm depends on several factors:
1) dose
2) heredity
3) other negative influences
4) age
 prescription and non-prescription drugs
o thalidomide
o DES (diethylstilbestrol)
 DES daughters are more likely to miscarry or
delivery too early.
 DES sons may display a greater vulnerability to
fertility problems and immune problems.
o Aspirin
o Caffeine
o Cocaine, heroin, methadone
o marijuana
o tobacco
o Alcohol: fetal alcohol syndrome, fetal alcohol effects
 no amount of alcohol during pregnancy is safe.
 Radiation
 environmental pollution
 infectious disease:
o rubella
o HIV
o herpes viruses (cytomegalovirus, herpes simplex 2)
o toxoplasmosis
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Lifespan overheads, chapter 3: prenatal development, birth, and the newborn
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Other maternal factors
 exercise
 nutrition (e.g. folic acid)
 emotional stress
 Rh blood incompatibility
 maternal age and previous births
Childbirth
3 stages of childbirth:
 1st stage  dilation and effacement of the cervix
 2nd stage  birth of the baby
 3rd stage  delivery of the placenta or afterbirth
Baby’s adaptation to labor and delivery:
 force of contractions makes babies produce stress hormones:
o help withstand oxygen deprivation by sending more
blood to heart and brain
o causes lungs to absorb excess liquid
o makes the baby alert, ready to greet the world!
 average baby is 20 inches long and 7 ½ pounds at birth
Assessing the newborn’s physical condition
Apgar test
 heart rate (absent = 0; slow = 1; over 100 beats per minute = 2)
 respiration (absent = 0; slow = 1; good, crying= 2)
 muscle tone (0= limp; 1= weak, some flexion; 2= strong, active)
 colour (0=blue; 1= pink body, blue extremities; 2= pink)
 reflexes (0=no response; 1= frown/grimace/weak cry; 2=
vigorous cry/cough/sneeze)
 score of 7 or higher at the 5 minute test are considered in ok
condition
 4 or lower means trouble
Lifespan overheads, chapter 3: prenatal development, birth, and the newborn
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Approaches to childbirth
 natural childbirth (a.k.a. prepared childbirth)
o Classes
o Relaxation and breathing techniques
o Labor coach
 home delivery
 for healthy women who are assisted by a doctor or midwife, this
is as safe as a hospital birth
 but if attendants aren’t well trained in the event of an
emergency, the rate of infant death is high
Medical interventions
 fetal monitoring
o Abnormal heartbeat can mean the baby is in distress
 labor and delivery medication
o analgesics
o anesthetics
 weakens uterine contractions during the 1st stage of
labor and interferes with the mother’s ability to feel
contractions and push during the 2nd stage
 results in prolonged labor
 newborn will be sleepy and withdrawn, suck poorly
during feedings, and be irritable when awake
 cesarian delivery
o 30 years ago 3% of births; now 21%-highest rate in world!
o more time for recovery
o baby may be sleepy, withdrawn, irritable
Lifespan overheads, chapter 3: prenatal development, birth, and the newborn
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Preterm and low-birth-weight babies
 Preterm: born several weeks earlier than their due date. Weight
may be appropriate for time they spent in the womb
 Small for date: below their expected weight.
o the most serious problems
o death in 1st year; infections; brain damage
o lower intelligence test scores, less attentive
o inadequate nutrition before birth
 Preterm babies as a group are more at risk for child abuse.
 Isolette: controls temperature, sources of infection.
 respiratory distress syndrome: > 6 weeks early  serious
breathing difficulties
 stimulation: rocking, heart beat, mom’s voice, soft music,
promote weight gain, predictable sleep patterns, alertness
 massage
 parental training
Birth Complications
 Emmy Werner’s (1955) longitudinal study of infants with mild,
moderate, or severe birth complications.
o best predictor of how well they did in later years was the
quality of their home environments.
The Newborn’s capacities
Reflexes:
 eye blink
 rooting
 sucking
 swimming
 Moro
 palmar grasp:
 stepping
 Babinski
Lifespan overheads, chapter 3: prenatal development, birth, and the newborn
Newborn states:
1) regular sleep, 8-9 hours a day
2) irregular sleep, 8-9 hours a day. Includes REM sleep
3) drowsiness; varies from kid to kid
4) quiet alertness: 2-3 hors a day
5) waking activity and crying; 1-4 hours a day
 sleep:
o REM sleep: 50% of newborns’ sleep time!
o special need for cortical stimulation provided by REM.
 crying:
o physical needs: hunger, temperature, noise, pain.
o provokes feelings of arousal and discomfort in adults
Sensory capacities:
 touch: sensitivity to touch is well developed at birth, especially
around the mouth, palms, and soles of feet
o temperature change
o very sensitive to pain
 taste and smell: prefer sweet to salty. Expressions reveal
preferences.
o breast milk is ideally suited to support the infant’s early
growth.
o Babies like the smell of bananas, chocolate; do not like
rotten eggs
o preference for the smell of their mother’s amniotic fluid
o preference for the smell of their own mother’s breast
o preference for the smell of a lactating woman to formula
 hearing: newborns prefer voices and noises to pure tones.
They can tell the difference between sound patterns (ma, ba)
o prefer high-pitched voice, expressive, ends w. rising tone
 vision: least developed of the senses at birth.
o Poor visual acuity (20/600); tracking is slow, inaccurate
o Prefer colour rather than grey stimuli, but aren’t yet good
at discriminating among colours
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Lifespan overheads, chapter 3: prenatal development, birth, and the newborn
Neonatal Behavioural Assessment:
The Brazelton Neonatal Behavioural Assessment Scale (NBAS)
 some research findings:
o Asian and Native-American babies are less irritable than
Caucasian babies
o NBAS recovery curves predict intelligence with moderate
success well into the preschool years
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