Download PSYC 2314 Lifespan Development

PSYC 2314
Lifespan Development
Chapter 4
Prenatal Development and Birth
Stages of Prenatal Development
• Germinal period
– First two weeks
– Within hours after conception, the one-cell
zygote travels down the Fallopian tube toward
the uterus and begins the process of cell
division and growth
Stages of Prenatal Development
• Germinal period
– Soon, differentiation occurs, a process first
clearly seen when the multiplying cells separate
into two distinct masses, one inside the other.
The outer cells will become the placenta; the
inner cells form a nucleus that will become the
embryo.
– If all goes well, implantation of the cell mass
occurs.
Stages of Prenatal Development
• Embryonic period
– Begins as the organism begins differentiating
into three layers, each of which will become a
key body system.
– A fold in the outer layer of cells becomes the
neural tube, which will become the brain and
spinal column (the central nervous system).
Stages of Prenatal Development
• Embryonic period
– In the fourth week, the cardiovascular system is
functioning; the eyes, ears, nose, mouth start to form.
– At five weeks, the arm and leg buds appear and the
embryo is about ¼ inch long.
– By the end of the second month, the developing
organism weighs about 1 gram, is 1 inch long, and has
all the basic organs (except the sex organs) and features
of a human being.
Stages of Prenatal Development
• Fetal period
– During the third month, the sex organs begin to
take shape.
– During the early weeks of life, the placenta
develops rapidly. This organ connects the
circulatory system of the mother with that of
her growing embryo, allowing nourishment to
flow to the developing organism and
transporting wastes away.
Stages of Prenatal Development
• Fetal period
– In the mid three months, the systems develop more
fully. The crucial factor in the fetus’s attaining the age
of viability, beginning at about 22 weeks, is brain
maturation, which is essential to the regulation of the
basic body functions of breathing, sucking, and
sleeping.
– By 28 weeks, the typical fetus weighs about 1,300
grams (3 lbs.) and has a greater than 90 % chance of
survival.
Stages of Prenatal Development
• Fetal period
– During the last 3 months, the respiratory and
cardiovascular systems mature dramatically.
– Weight gain during last weeks stores fat, which will
provide a layer of insulation when the child is no longer
surrounded by the mother’s warmth. The weight gain
also provides nourishment and vitamins that will be
used until the mother’s breast milk is fully established.
Fetus’s Responses
• Physiological interdependence
• Fetal movements
• Hearing
Teratology
• The scientific study of birth defects
• A science of risk analysis, which attempts to
evaluate what factors can make prenatal
harm more, or less, likely to occur.
• Teratogens—substances or conditions as
viruses, drugs, chemicals, stressors, and
environmental hazards.
3 Crucial Factors
• Timing of exposure
• Amount of exposure
• Developing organism’s genetic vulnerability
to damage from the substance
Critical periods
• Physical structure and form-embryonic
• For conditions (such as severe malnutrition)
and substances (such as heroin), that disrupt
and destabilize the overall functioning of
the woman’s body, there are two critical
periods: the very beginning and the near
the end of the pregnancy
Critical periods
• At the very beginning, when stress during
the germinal period can impede
implantation.
• Near the end, when the fetus most needs to
gain weight and when the cortex of the
brain is developing, making the fetus
particularly vulnerable to damage that can
cause learning disabilities.
Critical periods
• Also, instability of the mother’s body
systems (chills, shakes, etc.) can loosen the
placenta or cause hormonal changes, both of
which can precipitate birth.
• For behavioral teratogens there is no safe
period. The brain and nervous system can
be harmed throughout the prenatal
development.
Amount of Exposure
• Threshold effect: the substance is virtually
harmless until exposure reaches a certain
frequency or dosage.
• Interaction effect: the combination of
threshold teratogens taken together may
make them more harmful at lower dosage
levels than they would be individually.
Genetic Vulnerability
• Susceptibility to alcoholism involves a genetically
related defect in a specific enzyme.
• A deficiency in folic acid in the mother’s diet may
also result in genetic defects.
• Males not only have a higher rate of teratogenic
birth defects and later teratogen-related behavioral
problems, but also a higher rate of spontaneous
abortions.
Teratogens
• Rubella (German measles)
– If contracted early in pregnancy, it can cause
blindness, deafness, heart abnormalities, and
brain damage.
• Human Immunodeficiency Virus (HIV)
– A pregnant women with HIV may pass the
virus on to her fetus either during pregnancy or
childbirth. Infants who have HIV will
eventually develop pediatric AIDS.
Teratogens
• Psychoactive Drugs
– Slow fetal growth, contribute to premature
labor, and may produce both short- and longterm brain deficits.
Teratogens
• Alcohol Consumption
– Large doses of alcohol can trigger the physical,
behavioral, and mental symptoms of fetal
alcohol syndrome (FAS).
– Even moderate alcohol consumption during
pregnancy (more than ½ ounce of absolute
alcohol) can produce the intellectual
impairment of fetal alcohol effects (FAE).
Teratogens
• Smoking
– Increases the risk of abnormalities and reduces
birthweight and size; babies whose mothers
smoked are shorter at birth and in the years to
come. They are also more likely to have
respiratory problems.
Teratogens
• Drugs
– Prenatal exposure to marijuana has been linked
to central nervous system impairment.
– Exposure to heroin causes slower fetal growth
and premature labor.
– Cocaine use during pregnancy retards fetal
growth, increase the risk of problems with the
placenta, and often leads to early learning
difficulties.
Protective Measurements
• Complete abstinence from drugs even
before pregnancy
• Abstinence after the first month
• Moderation throughout pregnancy (if
abstinence is not possible)
• Minimizing maternal stress by seeking
social support
• Obtain good postnatal care
Birthweight
• Low birthweight (LBW)
– Less than 5 ½ lbs.
• Preterm
– LBW infants who are born more than 3 weeks
early
• SGA (small for gestational age)
– Infants born close to the due date but weighing
less than most full-term newborns.
Poverty and LBW
• Pregnant women at the bottom of the SES are
more likely to be ill, malnourished, teenaged, and
stressed
• If they are employed, their jobs often require long
hours of physically stressful work, exactly the
kind that correlates with preterm and SGA
• They often receive late or inadequate prenatal
care, breathe polluted air, live in overcrowded
conditions, ingest unhealthy substances
Normal Birth
• Begins at about the 266th day after
conception, when the fetus’s brain signals
the release of hormones that trigger uterine
contractions in the mother.
• The first stage of labor (until the baby’s
head emerges from the birth canal) usually
lasts 6 hours in first births and 3 hours in
subsequent births.
Apgar Scale
• Used to assign score between 0 and 2 to the
newborn’s heart rate, breathing, muscle
tone, color, and reflexes at 1 minute after
birth and again at 5 minutes.
• A score of 7 or better indicates the newborn
is not in danger; below 7, infant needs help
in establishing normal breathing; and below
4, the baby is in critical condition.
Medical Attention/Intervention
• Medical procedures are overused:
episiotomies and C-sections
• Routine procedures: IV, fetal monitoring,
are rooted in tradition rather than in medical
necessity.
Birth Complications
• Birth complications are more likely if the fetus is
already at risk because of low weight, preterm
birth, genetic abnormality, or teratogenic
exposure.
• Researchers now realized that cerebral palsy
(difficulties with movement control resulting from
brain damage) results from genetic vulnerability,
worsened by teratogens and a birthing process that
includes anoxia (a temporary lack of oxygen).
Birth Complications
• Many hospitals now provide high-risk
infants with regular massage and soothing
stimulation.
• When they are brought home, high-risk
infants are often more distractible, less
obedient, and slower to talk. However,
long-term impairment is not inevitable.
Parent-newborn Bond
• Emphasize the tangible as well as the intangible
attachment of parent to child in the early moments
after birth.
• Diane Eyer-bonding is a social construction that
developed as a reaction against the medicalization
and depersonalization of traditional hospital births.
• Extensive research has shown that the events right
after birth are just one episode in a long-term
process of bonding between parent and child.