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5.1 Conception through Birth
5.1.1 Conception
Each
month during reproductive life, an ovary releases an ovum. The
ovum is captured by the fallopian tube. Conception
(fertilization) occurs when a sperm reaches and penetrates the
ovum to form a zygote. Sperms and ova are haploid, i.e., each
contains half the number of chromosomes in a body cell (23). The
zygote is diploid, i.e., it contains the full complement of
chromosomes (46 for the human cell).
As the
zygote moves to the uterus, it divides repeatedly to form the
embryo: a cluster of developing cells that, by one week after
conception, attaches (implants) itself into the wall of the
uterus. The placenta is the organ that anchors the embryo to the
uterus. The umbilical cord connects the embryo to the placenta.
Oxygen and nutrients reach the embryo from the mother through
the umbilical cord. The cord also moves wastes from the embryo
to the mother to be excreted from her body.
A
blocked fallopian tube can result in an ectopic pregnancy, i.e.,
growth of a fertilized egg outside the uterus, e.g., in the
fallopian tube; the tube can then rupture leading to
life-threatening internal haemorrhage. Occasionally a twin
pregnancy occurs. Twins may be identical or fraternal. In the
former, a zygote splits in half and each half forms an embryo.
Fraternal twins come from different eggs and sperms and thus
have different chromosomes.
5.1.2 Prenatal
Development
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The first trimester.
The embryo is recognizable as a human fetus by the end of
the second month.
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The second trimester.
Muscles develop. The fetus begins to move (quickening). The
fetus is almost completely developed by the end of this
trimester.
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The third trimester.
By the end of 9 months, or fortieth week, the fetus is ready
to be born.
5.1.3 Factors that
Influence Prenatal Development
·
The mother’s health status, diet, life style and prenatal care are
important. Early and regular medical care by an obstetrician is
essential. Blood pressure, weight, urine analysis, information
about pregnancy, and the position and growth of the baby are
among the items checked regularly.
·
Good nutrition promotes a healthy pregnancy. Adequate amounts of
protein, calcium, iron, and vitamins A, B, C, and D are
important. Poor nutrition can lead to slower fetal growth,
premature delivery and low birth weight with increased risk to
the baby. Alcohol and smoking should be discontinued. All drugs
should be avoided except those prescribed by the physician.
Ingredients of drugs, inhaled cigarette smoke, and alcohol can
cross from the mother’s bloodstream to the baby’s and cause
harm.
·
Proper medical care can detect, prevent and/or treat problems associated
with some pregnancies:
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Toxemia of pregnancy: sudden rise of blood pressure,
protein in the urine and increased body water (oedema), after
the twentieth week.
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Birth defects may result from drugs, poor dietary habits,
or an infection, e.g., rubella, during pregnancy or may be
genetic.
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Genetic counseling can advise couples with a family
history of genetic disease about their chances of producing
offspring with birth defects.
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Ultrasound and amniocentesis can detect birth defects.
Amniocentesis is the aspiration and analysis of some of the
fluid that bathes the fetus in the uterus. It is performed after
the sixteenth week after the position of the baby is determined
by ultrasound.
-
Anti-rhesus vaccine given to a rhesus-negative mother
immediately after birth of a rhesus positive baby will prevent
damage to the red blood cells of another rhesus positive fetus
in the next pregnancy.
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Premature babies weigh less than 2.5 kg at birth. Mothers
at risk can wear a monitoring device around the waist to warn
them when early signs of labor occur. They can be rushed to
hospital and given medication to stop labor so that the baby
will have more time to continue to develop.
5.1.4 Birth
At
birth the baby is pushed out of the uterus by rhythmic
uterine contractions that grow stronger and faster while the
cervix dilates. Once delivered, the baby’s mouth is suctioned to
remove mucus. The baby starts to cry and, once breathing on its
own, the umbilical cord is clamped and cut off. The remaining
stub will fall off in a few days.
If the
baby cannot pass through the vagina, e.g., because it is
too large or not correctly positioned, a caesarian section
is performed.
The
postpartum period may last several weeks. It is marked by
hormonal changes in the mother’s body and the secretion of milk
from the breast. Breast-fed babies seem to have fewer cases of
respiratory illnesses, skin disorders, constipation and
diarrhea, and are less likely to gain excess weight in later
life.
5.1.5 Infancy through
Adulthood
Stages of Development
Growth
and development occur in fairly predictable stages. Specific
skills and experiences are acquired at each stage which prepares
the child for dealing with the problems and challenges of the
next stage.
a- Infancy
Infancy is the period from birth to one year. It is
characterized by rapid growth, eruption of teeth,
coordination of the muscular and nervous system, with the
ability to sit, stand, and reach for objects. The infants
learn about themselves and explore their environment, especially
when they begin to crawl.
b- Childhood
Childhood is the period between the end of infancy and the
beginning of puberty. it is characterized by steady
physical growth, bowel and bladder control and refinement of
communicative skills of writing and speaking. Exposure to
caring and loving people is important to foster a sense of
acceptance, worth, and self-esteem.
Self-esteem is developed as abilities are acquired. Many
children appreciate having responsibilities which show that they
can care for themselves and others within the family, e.g.,
putting away their toys, making up their beds, setting or
clearing the table when they are able. Decision making also
develops during childhood. Children learn to decide for
themselves, e.g., what will I wear today? Decisions are not
always responsible and parental guidance is needed. Feelings of
competence are acquired through the ability to do work and to
read which makes children begin to understand a few of the
complexities of the world.
c- Adolescence
Adolescence is the period between infancy and adulthood,
generally between the ages of 12 to 19. It is
characterized by a growth spurt – earlier in females (11-13
years) than in males (13-15 years) – and appearance
of secondary sex characteristics. Questions are raised such as “who
am I?”, “what do I want to be?”, and what do I believe?”
More independence from parents is sought and the influence of a
peer group can be significant. Most adolescents, however, will
agree with their parents’ ideas and share their values.
Parents can contribute to a healthy adolescence by 1) allowing
children to develop independently, feel secure and practice
self-discipline early in life, and 2) maintaining contact with
their children by developing an interest in their activities and
demonstrating trust and approval.
d- Adulthood
Adulthood is the period from adolescence through old age. Adults
do not change much physically over the years, and they can stay
fit into old age if they exercise regularly and adopt healthful
lifestyles. Psychosocial changes, however, occur:
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Early adulthood (third decade), is characterized by
independence, and self-responsibility. Intimate relations are
sought.
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Middle adulthood (fourth decade) is marked by adjusting life
goals and seeking standards, e.g., quitting an unsatisfactory
job and looking for a new one.
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Late adulthood is often the most stable period of the life
cycle with people looking back with satisfaction at what they
have accomplished. However, it could be a depressing time for
people who have not achieved a sense of closeness with others
and who feel they have no control over their destiny. |