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Child Development - A Thematic Approach
, Fifth Edition
Danuta Bukatko - College of the Holy Cross
Marvin W. Daehler - University of Massachusetts, Amherst
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| | Chapter Outline
Chapter 4:
The Prenatal Period and Birth
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The stages of prenatal development
Prenatal development is the period of time from conception to birth when the developing individual
undergoes a series of transformations from a single-celled zygote, to an embryo, to a fetus. The period of time
from about the seventh month of pregnancy to twenty-eight days after birth
is the perinatal period. Postnatal development begins once the baby is born.-
Fertilization
Fertilization can take place when a mature egg cell, or ovum, is released
from the female's ovary into the Fallopian tube and male sperm cells are present. A successful
sperm cell will penetrate the egg cell, and the chromosomes of the sperm and egg will combine to form a fertilized
egg, called the zygote, which contains the full forty-six chromosomes necessary
for further development. If unfertilized, the ovum survives only about 24 hours. -
The germinal period
Within a day of fertilization, the newly formed zygote migrates down the
fallopian tube and begins a series of mitotic cell divisions called cleavages
to form the morula, a solid sphere of sixteen cells. Each cell has the identical ability to become a separate organism, because
at this early stage the cells are undifferentiated. The cells begin to differentiate
when they segregate into an outer and an inner layer of cells collectively
called the blastocyst. The blastocyst implants itself in the lining of the uterus about ten days
following conception. An ectopic pregnancy occurs if the zygote implants somewhere other than the uterus. Such pregnancies
are normally terminated because of the enormous risk they pose for a pregnant woman. -
The embryonic period
Following implantation of the blastocyst, a three-layered embryo is formed.
The endoderm or inner layer will become the lining of most inner organs,
and the mesoderm will become the skeletal, muscular, and cardiovascular systems. The
mesoderm, or middle layer develops into the skeleton and muscles. Finally,
the ectoderm or outer layer, forms the neural tube, which will develop into
the spinal cord, nerves, and brain. Anencephaly and spina bifida are abnormal conditions in which the cephalic
region or the caudal region of the neural tube, respectively, fails to close,
resulting in death or severe nervous system damage. -
The fetal period
The fetal period begins at eight weeks, when bone starts to form, and ends
at birth. The fetus is recognizably human early in this stage, and most structures
and organs have already formed. The second trimester, or second three months of the pregnancy, is characterized
by rapid growth in body size, and the mother can begin to feel fetal movements,
called quickenings. During the final three months of pregnancy, the third
trimester, the brain continues to undergo considerable development. Sensory systems develop and
the fetus is now capable of smelling, tasting, hearing, seeing, and feeling.
In the third trimester the fetus attains viability, the ability to survive outside the womb. Gestational age is counted from the first day of the mother's last menstrual period. Birth typically occurs when the fetus reaches 277
gestational days. -
Assisted reproduction
For many prospective parents who cannot conceive normally, a number of alternatives exist for having a child. These include
artificial insemination by donor, a method by which the sperm of a donor
male (often anonymous) is artificially provided to a woman; egg donation,
a method by which an egg of a female (often anonymous) is made available to a woman; gamete intrafallopian
transfer, insertion of sperm cells or an egg cell in a woman's Fallopian tube to permit fertilization (or a zygote in the case of zygote
intrafallopian transfer); in vitro fertilization, the fertilization of an egg by sperm in vitro and its subsequent implantation
in the uterus; and surrogacy, a contractual arrangement in which another
woman carries the pregnancy to term for a couple. Such procedures are expensive
and are often accompanied by increased legal, medical, and social risks. Nevertheless, a large
number of children are now conceived through assisted reproduction. No evidence
exists to suggest that the physical or psychological risks to children born
through assisted reproduction are any greater than for children conceived normally except for that
associated with the increased risk of multiple pregnancy which often accompanies
in vitro fertilization.
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Environmental factors influencing prenatal development
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Support within the womb
The placenta is a network of blood vessels and capillaries, some originating from the
mother and some from the fetus. It is the site where nutrients and waste products are exchanged between the maternal and fetal blood
systems. The umbilical cord transports nutrients and waste products between the fetus and placenta. The amniotic sac is a fluid-filled membrane surrounding the fetus, protecting it from bumps and shocks. -
Principles of teratology
Teratology is the study of birth defects that result from environmental
causes. Environmental agents that cause such disruptions are known as teratogens. Convincing evidence of the effects of environmental agents on the developing
embryo and fetus came from mothers who used thalidomide during pregnancy.
Thought to be a harmless drug, thalidomide caused severe malformations of
the arms and legs in infants who had been exposed during early prenatal development. Research has revealed
several principles of teratology:
- The principle of susceptibility
- The principle of critical or sensitive periods
- The principle of access
- The principle of dose-response relationships
- The principle of teratogenic response
- The principle of interference with specific mechanisms
- The principle of developmental delay and "sleeper effects"
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Drugs as teratogens
Prenatal exposure to alcohol, in its most severe form, causes fetal alcohol syndrome (FAS), which results in infants born with some physical abnormalities and mild to
moderate mental retardation. Even casual use of alcohol has been found to
lead to alcohol-related neurodevelopmental disabilities (ARND) in which children exhibit learning
difficulties and behavioral problems. Cigarette smoking has been linked to
increased rates of fetal and infant mortality. The most consistent effect
of smoking on the developing fetus is lower birth weight. The effects of over-the-counter and prescription
drugs on prenatal development are less clear-cut. Medical professionals recommend
that pregnant women take no drugs. The effects of illegal drugs such as heroin,
marijuana, and cocaine on the developing human embryo and fetus have been less conclusively
demonstrated, largely because of methodological problems with this research
that can confuse drug effects with malnourishment, smoking, drinking alcohol,
receiving poor prenatal care, and an inadequate postnatal environment for the infant. High-quality postnatal
care can help to counter many of the negative effects believed to be caused
by drug exposure.
Controversy: Should a Drug-Abusing Expectant Woman Be Charged with Child Abuse?
What are an expectant woman's legal and moral responsibilities to the fetus? Should expectant women who
use drugs be punished as criminals, or does the woman's right to privacy and her need for treatment make such an approach inappropriate? |
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Diseases as teratogens
Exposure to rubella (German measles) during the first trimester can result
in growth retardation, cataracts, hearing deficits, heart defects, and mental retardation in the
infant. A parasite found in cat feces or raw and partially cooked meats cause
toxoplasmosis. The effects of the disease on the fetus, which are most devastating
if it is contracted early in the pregnancy, include growth retardation, excess fluid in the brain,
and CNS damage. Cytomegalovirus is the most common source of infection for
newborns and can have a devastating effect on infant development if contracted
prenatally. Sexually transmitted diseases such as herpes, chlamydia, gonorrhea, syphilis, and AIDS
either disrupt conception or pregnancy or are transmitted to the fetus. In
the case of AIDS, infants who acquire the disease during prenatal or perinatal
exposure to HIV can show poor growth and motor and mental retardation. However, new medical treatments
are helping to delay the onset of impairments as well as helping to reduce
the transmission rate from mother to offspring, and the transmission of HIV/AIDS
from mothers to infants has declined over the past several years. -
Environmental hazards as teratogens
Radiation, lead, carbon monoxide, and many other chemicals can cause birth
defects, particularly if the embryo or fetus is exposed during early prenatal development. -
Women's conditions and prenatal development
In addition to teratogens, a number of health conditions are associated
with prenatal risk factors. The likelihood of having a child with Down syndrome, a premature infant, and a difficult labor increases
as maternal age advances past thirty-five. Teenage mothers are at even greater
risk because they are less likely to receive adequate prenatal care. Malnutrition
early in pregnancy can lead to spontaneous abortions, stillbirths, and nervous system damage.
When occurring later in pregnancy, malnutrition is associated with reduced
fetal growth and low birth weight. According to some research, maternal stress
may complicate a pregnancy by affecting hormone levels and blood flow to the placenta and by increasing
the use of cigarettes, alcohol, and drugs, resulting in low birth weight
and respiratory difficulties. However, a supportive social environment helps
to mitigate many negative effects of stress. -
A final note on environment and prenatal development
It is important to note that although many environmental and maternal factors
may be teratogenic, between 90 and 95 percent of babies in the United States are born well and develop normally.
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Birth and the perinatal environment
Societal rituals and childbirth practices vary and affect how childbirth
is perceived and how effortlessly it progresses. Some societies see birth as a natural and healthy process; other societies
view birth as requiring medical care and attention.-
Preparing for childbirth
Concerns over the effects of drugs on fetal development have led to methods of prepared (natural) childbirth, which aim to teach women to relax and to understand the changes that occur
during labor and childbirth and encourage a cooperative relationship between
doctor and patient during the childbirth experience. A desire to create a more relaxed and natural setting
for childbirth has led to more and more infants being born at home or in
freestanding birthing centers (FSBCs). Women considered at risk for any perinatal
problems, however, are encouraged to use hospitals for their deliveries.
Research Applied to Parenting: Nurturing and Caring During Labor
With the relocation of childbirth to hospitals in many societies, women became
isolated from supportive family and friends and became less active in decision making about childbearing. Research indicates
that women who have a supportive partner or trusted companion available during
labor spend significantly less time in labor, require fewer drugs, and have
babies who show less fetal distress than women who have routine nursing care. In addition to
doctors, midwives and others trained in childbirth can assist in delivery
and may even help to reduce the need for medical intervention. Alternative
ways to deliver the baby may also increase comfort during childbirth and reduce stress on the infant. |
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Labor and delivery
Labor begins with the onset of regular, increasingly frequent contractions.
There are three stages of labor. In the first stage, uterine contractions
and dilation of the cervix permit descent of the baby down the birth canal. Continued descent and the birth of the
baby occur in the second stage, and expulsion of the placenta occurs in the
final stage. Controversy continues to exist about the consequences of medication
to the child during childbirth. A cesarean birth is delivery through a surgical incision made in
the woman's abdomen and uterus. The availability of fetal monitoring devices to monitor fetal stress, concerns about birth trauma such as anoxia, and
risk of infection from sexually transmitted diseases have contributed to the increase in the cesarean rate
in the last decade, particularly in the United States. -
Low birth weight
Infants born weighing less than five-and-a-half pounds are considered to be low birth weight. As birth weight decreases, the likelihood
of death in the first few weeks of life increases significantly. Low-birth-weight
infants are at risk for respiratory difficulties, neurological difficulties,
hyperactivity, greater frequency of illness, and disruption of family functioning. A distinction
is made between low-birth-weight infants who are preterm (less than thirty-five
weeks' conceptual age) and those born nearer to term (thirty-eight to forty weeks)
but who are small for gestational age (SGA). Efforts to reduce the problems associated with
low birth weight have been aimed at improved monitoring of infants' perinatal status and improved prenatal care, particularly for mothers at
risk. Various attempts have been made to give low-birth-weight infants either compensatory experience to duplicate
conditions in the womb or enriching stimulation that simulates the experiences
of the healthy newborn. Studies have reported at least temporary benefits
from both types of extra stimulation, the most consistent of which is increased weight gain and shorter
hospital stays. Kangaroo care, the newest form of prenatal caregiving includes both compensatory and enriching
elements.
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The newborn
The newborn infant, if delivered vaginally, will have a flattened nose and misshapen
head as a result of the pressure on the bones of the skull during the passage
through the birth canal. The skin is covered with vernix caseosa, an oily,
cheeselike substance that protects against infections. The first task of the newborn is to begin
breathing with its lungs. The umbilical cord is cut, severing the connection
between the newborn and the placenta. Next, the newborn must regulate its
body temperature. An external heat source or close contact with their mothers can help newborns maintain
their body temperature. Newborns typically weigh 5-and-a-half to ten pounds
and measure eighteen to twenty-two inches in length.-
Assessing newborns
The newborn is assessed immediately after birth using the Apgar Scale, which
provides a measure of the baby's vital signs. The Neonatal Behavioral Assessment Scale (NBAS) evaluates
the newborn's neurological condition and can predict developmental outcomes in the first few months of life. -
Newborn states
The newborn spends a great portion of the day sleeping and displays a wide
range of states, from drowsiness to regular or irregular sleep, alert activity, alert inactivity, and crying. The sleep patterns
of infants are dictated to a certain extent by cultural differences. Infants
display two distinct sleep states. REM (rapid-eye-movement) sleep is an active
sleep that includes muscle jerks and irregular breathing and heart-rate activity. NREM (non-REM)
sleep is a quiet sleep in which few movements and more regular heart rate
and breathing are present. Autostimulation theory suggests that REM sleep
provides the infant's central nervous system with essential amounts of stimulation that the infant may miss
by not being awake for long periods of time.
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