Pre-natal Development: Stages, Critical Periods, Factors and Educational Implications…


Pre-natal Development: Stages, Critical Periods, Factors and Educational Implications…

The word pre-natal means the period of development before birth. Conception takes place when a male sperm cell unites with or fertilizes the female egg cell. Conception marks the beginning of the pre-natal period of development.

The pre-natal period of development spans approximately nine calendar months or 265 days (plus or minus 14 days) of rapid growth and development. Individual differences may, however, occur in the length of the pre-natal period. The shortest time for the fetus to be born alive is 180 days. The longest time, regarded as the legal limit of post-maturity, is 334 days.

At the end of this page, you will be able to:

· Outline the three major stages in pre-natal development

· Describe the critical periods in pre-natal development

· Explain why some periods in pre-natal development are regarded as critical

· List at least five factors that influence pre-natal development

· Discuss the educational significance of pre-natal development.


Stages in Pre-natal Development

The pre-natal period consists of three distinct stages, namely: the germinal, the embryonic and the fetal stages. We discuss each of these stages in more detail.

1. The Germinal Stage (Fertilisation to 2 weeks): The germinal stage starts when the male sperm cell fertilises the female egg cell. It is the shortest stage of the pre-natal period of development.

It lasts for about two weeks following conception. During this stage, the new organism, now called the zygote travels towards the uterus. On reaching the uterus, the zygote becomes implanted in the wall of the uterus. The wall of the uterus is very rich in nutrients which nourish the zygote.

During the germinal stage, significant changes occur in the internal structure of the zygote. The stage is characterised by rapid cell division.

In addition to increasing number, the cells of the zygote become increasingly specialised. The mass of cells separate into the outer and inner parts. Some of the cells form a protective layer around the mass of cells. Others begin to establish the rudiments of a placenta and the umbilical cord. When fully developed, the placenta serves as a conduit between the mother and the developing organism. The placenta provides nourishment and oxygen via the umbilical cord. Also, waste materials from the developing child are removed through the umbilical cord.

2. The Embryonic Stage (2 weeks to 8 weeks): The stage of the embryo starts from the end of two weeks after conception and extends to the end of the second month. By the second week the organism had become firmly secured to the wall of the mother’s uterus. At this point, the child is called an embryo.

The major highlight of this stage is the differentiation and development of the major organs and the body systems. The embryonic disc first differentiates into three layers: the ectoderm, the mesoderm and the endoderm. Each of these forms a different set of structures as development unfolds.

· The Ectoderm. The outer layer is the ectoderm. The ectoderm forms the epidemis of the skin, hair, nails, teeth, sense organs, the brain and the spinal cord.

· The Mesoderm. The middle layer is the mesoderm. The mesoderm produces the dermis or the inner layer of the skin, the muscle, bones, blood, the circulatory system and the reproductive system.

· The Endoderm. The inner-most layer is the endoderm. The endoderm produces the digestive system, the pancreas and the thymus.

Every part of the human body is formed from the three layers of the embryo mentioned above. The stage of the embryo is characterised by very rapid and orderly changes.

By the end of the embryonic stage the organism resembles a miniature human being. All the basic organs and features of the human being have been formed. However, the sex of the baby cannot be known at this point. Beyond this stage, no other changes in the features take place.

The only further changes are in the relative size of the different parts of the body.

3. The fetal Stage (8 weeks to birth): The fetal stage is the longest stage in the pre-natal period of development. During this stage, the child is instantly recognisable. The stage starts at about 8 weeks after conception and continues until birth.

The organism, now called the fetus, undergoes outstandingly rapid changes. It increases in length about 20 times. Its proportions also change dramatically. At about the beginning of the fetal stage, the head is about one-half of the fetal size. At the time of birth, the fetal head is only about one quarter of the total size of the fetus.

The fetal stage witnesses increased complexity of the organs and systems. The organs and systems become more differentiated and operational. For example, at 3 months, the fetus swallows and urinates.

Arms develop hands. Hands develop fingers. Fingers develop nails.

At this period, the fetus makes itself known to the outside world. It becomes increasingly active. By 4 months, the mother can feel the movement of the fetus. A wide range of fetal activities become noticeable.

The fetus can now turn, do somersaults, cry, hiccup, clench its fist, open and close its eyes and suck its thumb.

 The fetus responds to a variety of sensory stimulation such as: taste, smell, sight, touch and sound. Indeed, it has been reported that the fetus heard and responded to sounds it had heard repeatedly.

During the third trimester, the brain grows rapidly, expanding its abilities. The heart and lungs strengthen, making it possible for the fetus to survive on its own if birth comes. The fetus stops growing about 5 to 7 days before birth. It drops into position for delivery. A good number of normal, full-term fetuses end in birth 259 to 273 days after fertilization .

 We note that good nutrition on the mother’s part increases the chances of normal delivery, and a healthy baby.


Critical Periods in Pre-natal Development

Critical periods in pre-natal development refer to periods when delicate and important organs and systems of the body are being formed. These periods are considered critical because if the uterine environment is not conducive major structural abnormalities or pre-natal death occur.

Such abnormalities may include central nervous system deformities, organ or system deformities involving the heart, arms, legs, eyes, teeth, palate, external genitalia, or the ear. The effect of adverse uterine environment is most potent at the critical periods of pre-natal development.

The critical periods are: the first trimester or the first three months after conception, the seventh month, and the ninth month. We discuss in more detail each of these critical periods.

· The First Trimester

As has already been noted, the first three months of pregnancy includes the germinal and embryonic stages of pre-natal development. During this period, delicate organs and systems of the body form and differentiate. Structural abnormalities and physiological defects of the heart, the central nervous system, the spinal column, the eyes, the ears, the arms and the limbs are most likely to occur during the first trimester.

· The Seventh Month

By the seventh month of pregnancy, the fetus would have attained sufficient development to be viable. The fetus has a chance of survival outside the uterus if delivered pre-term. For a pre-term baby to survive, the central nervous system and the brain must have developed sufficiently to support partial regulation of breathing, swallowing and body temperature. If for whatever reason, the brain and the nervous system failed to complete their development, a pre-term baby will be negatively affected.

· The Ninth Month

By the end of nine calendar months or approximately 280 days of pregnancy, a child should be delivered without much problem.

However, environmental conditions could introduce complications and make the birth process problematic.

Conditions such as a weak womb, a narrow pelvis, improper position of the fetus, maternal illness or malnutrition could result to prolonged labour. A convergence of several health factors, namely: poverty, poor antenatal care, low levels of immunisation and unsanitary delivery conditions make the ninth month and the birth process a very critical period in developing countries.


Factors influencing Pre-natal Development

Fetal environment exert significant influence on fetal development. The degree of influence depends on the nature of the factor, the intensity and the time of exposure to factors. Among the factors are the following: mother’s diet, mother’s age, mother’s illness and mother’s drug use.

Mother’s Diet

A mother’s diet plays an important role in sustaining the rapid development of the fetus during the pre-natal development. Studies indicate that a mother who takes diet high in nutrients has fewer complications during pregnancy. Labour is also easier, and the baby generally healthier than a baby whose mother had a diet poor in nutrients.  It has been reported that protein and vitamin deficiencies in the mother’s diet can result to eye and internal organs defect, and an increase in a number of malformation of the baby.

Mother’s Age

The age of the mother at conception is an important factor that influences pre-natal development. Babies born to teenage mothers are exposed to greater risks than babies born to mothers in their twenties.

The mortality rate of infants and premature deliveries are higher in babies born to adolescent mothers than in babies born to mothers in their twenties.

Furthermore, the risks involved in pregnancy are greater, not only for teenage mothers, but also for unusually old mothers. Older mothers are more likely to give birth prematurely, and their children are more likely to have low birth-weights. The incidence of children with Down Syndrome, a form of mental retardation, is more among mothers who are more than 40 years at the time of conception.

Mother’s Illness

Infectious diseases abound in the African environment. This is more so in the slum areas of the cities. These diseases include: rubella virus, genital herpes, human immuno deficiency virus (HIV), some sexually transmitted diseases such as: syphilis and gonorrhea; chicken pox, measles, tuberculosis, polio, cholera, leprosy and others.

When a pregnant woman contracts any of these diseases, it may not only affect her health, but it may also be transmitted to the unborn baby.

Depending on when it strikes, an illness in a pregnant woman can have very serious consequences for the unborn baby. The onset of rubella in the mother prior to the 11th week of pregnancy is likely to cause in the baby blindness, deafness, heart defects, or brain damage.

Chicken pox may produce birth defects. Infants born to mothers with

HIV/AIDS (Acquired Immune Deficiency Syndrome) may have birth abnormalities, including small, misshapen faces, protruding lips, and brain deterioration.

Mother’s Drug Use

Mother’s use of drugs poses risks to the unborn child. Even drugs prescribed by medical professionals have sometimes posed serious consequences. In the 1950’s, many women who were told to take thalidomide for morning sickness during their pregnancies gave birth to children with stumps instead of arms and legs.  The physicians who prescribed the drugs did not know that the thalidomide inhibited the growth and development of limbs that normally would have occurred during the first three months of pregnancy.

Pregnant mothers who used illicit drugs such as marijuana and cocaine gave birth to infants who are irritable, nervous, and easily disturbed.

In particular, cocaine use was found to produce intense restriction of the arteries leading to the fetus, causing a significant reduction in the flow of blood and oxygen. This process increased the risk of fetal death.

Also, mother’s use of alcohol and tobacco can have profound consequences for the unborn child. Studies have found that children whose mothers consumed substantial quantities of alcohol during pregnancy had below average intelligence and had problems in behavior and other psychological functioning.

 It is because of the risks associated with alcohol and tobacco smoking that physicians today counsel pregnant women to avoid any alcoholic beverages and tobacco smoking.


Educational Implications

The knowledge of the developmental process that takes place during the prenatal period is important for the following reasons:

· The uterine environment plays a significant role in shaping the course of development during pregnancy and after birth.

· The presence of teratogenic agents in the uterine environment has the most profound consequences on the child. A teratogen is an environmental agent such as drug, chemical, virus, atomic radiation, or other factor that produces a birth defect.

· The timing of exposure to a teratogen is important. At some state of prenatal development, exposure may have minimal effect; at some other stage, exposure may have profound effect. For example, the child’s brain is most susceptible to teratogen from 15 to 25 days after conception. The heart is most vulnerable from 20 to 40 days following conception.

· There is need to create awareness on the effects of teratogenic agents on children before and after birth for the benefit of women expecting to have babies. There is need to optimize the prenatal environment.

· Prescribed caregivers should be sensitive to signs of behavior problems, and malfunctioning of organs and body systems of children. Early detection of abnormalities helps in appropriate referral and adequate intervention.

Prenatal describes the pre-birth (before-birth) journey of the child. Every child begins this journey as a single cell, much less than a dot.

Very complex transformations and very rapid growth occur during the prenatal stage of development. However the pre-birth journey of the child ends depends on a number of factors, including the mother’s health, genetic influences, and forces in the environment outside the life of mother and child.

The prenatal period is crucial because its challenges continue to influence future physical characteristics and psychological abilities of the individual. As a child caregiver, you are invited to be aware of the challenges of this period of the child’s life.

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