CHARACTERISTICS OF THE PRENATAL PERIOD
This is the first developmental period in the life span, though the period is short it is in many respects one of the most important period. It begins at conception and ends at birth approximately 270 to 280 days in length or of calendar 9 months. This has six important characteristics.
Although it is relatively short, the prenatal period has six important characteristics, each of which has a lasting effect on development during the life span. They are
The hereditary endowment which serves as the foundation for later development is fixed once and for all, at this time. While favourable or unfavourable conditions both before and after birth may and probably will affect to some extent the physical and psychological traits that make up this hereditary endowment, that changes will be quantitative and not qualitative.
Favourable condition in the mother's body can foster the development of hereditary potentials while unfavourable conditions can stunt their development.
The sex of the newly created individual is fixed at the time of conception and conditions within the mother's body will not affect it.
Proportionally greater growth and development take place during the prenatal period than at any other time throughout the individual's entire life. During these nine months, the individual grows from a microscopically small cell to an infant who measures approximately twenty inches in length and weigh on an average 3-3.5 kg. Development is rapid.
The prenatal period is a time of many hazards, both physical and psychological. This can have a marked effect on the pattern of later development or may even bring development to an end.
How life begins - New life begins with the union of a male sex cell and a female sex cell. These sex, cells are developed in the reproductive organs. There are twenty three pairs of chromosomes in each mature sex cell and each chromosome contains genes - the true carriers of heredity. At the time of conception four important conditions are determined that influence the individual's later development.
The four important conditions are
Hereditary endowment is the determination of the newly created individual's hereditary. Hereditary places limits beyond which individuals cannot go and it is entirely a matter of chance in the number of chromosomes from the maternal or paternal side that will be passed on to the child.
Sex - Determination of sex is the second important happening at the time of conception. Sex depends on the kind of spermatozoon that unites with the ovum.
Number of offsprings - when a ripe ovum is fertilized by one spermatozoon, the result will be a singleton, unless the fertilized ovum splits into two or more distinct parts during the early stages of cell cleavage, when this happens, the result will be identical twins, triplets or other multiple births. When two or more ova are released simultaneously and are fertilized by different spermatozoa, the result will be non identical twins, triplets or other multiple births.
Ordinal position - The fourth thing happening at the time of conception is the establishment, of the new child's ordinal position among siblings, such as the role the individual plays in the family and the treatment received from significant family members and their attitudes.
Developmental Lag in physical, mental, motor, and speech development. Twins tend to lag behind singletons of the same age. Lag in motor and speech development is also seen. This lag may be due to brain damage or to prematurity but it is more likely to be due to parental over protectiveness.
Twins tend to be smaller, age for age, than singletons. This is generally due to the fact that they are premature. They also suffer from brain damage and other physical defects more often than singletons.
Mental similarities between identical twins are much greater than between nonidentical twins and this persists into old age. Identical twins also show strong similarities in terms of special abilities, such as musical and artistic aptitudes.
Twins tend to compete for adult attention, to imitate each other's speech and behavior, and to depend on each other for companionship during the preschool years. As they grow older, sibling rivalry and competition develop. One twin usually takes on the role of leader, forcing the other into the role of follower. This affects their relationships with other family members and with outsiders.
Many twins have difficulty in developing a sense of personal identity. This is especially true of identical twins and of nonidentical twins of the same sex. Others enjoy the close relationship of twinship and the attention they receive as a result by their similarity in appearance. This leads to self-satisfaction and self-confidence.
Behavior problems have been reported to be more common among twins than among singletons of the same ages. It is thought that this is a result of the way twins are treated, both at home and outside the home. Behavior problems have also been reported to be more common among nonidentical than among identical twins. It has been suggested that this is because rivalry is stronger between nonidentical than identical twins.
It was interesting to read on the common characteristics of twins. Now let us analyse the three periods of prenatal development.
The prenatal period is ten lunar months of twenty eight days each in length or nine calendar months. This can vary from 180 to 334 days. Because prenatal development is orderly and predictable, it is possible to give a timetable of the important development taking place during this period. This period is divided into three stages.
The size of the zygote - that of a pinhead - remains unchanged because it has no outside source of nourishment; it is kept alive by yolk in the ovum.
As the zygote passes down the fallopian tube to the uterus, it divides many times and separates into an outer and an inner layer.
The outer layer later develops into the placenta, the umbilical cord, and the amniotic sac, and the inner layer develops into a new human being.
About ten days after fertilization, the zygote becomes implanted in the uterine wall.
The embryo develops into a miniature human being.
Major development occurs, in the head region first and in the extremities last.
All the essential features of the body, both external and internal, are established.
The embryo begins to turn in the uterus, and there is spontaneous movement of the limbs.
The placenta, the umbilical cord, and the amniotic sac develop; these protect and nourish the embryo.
At the end of the second prenatal month, the embryo weighs, on an average,33 gm (11/4 ounces ) and measures in length 11/2inches.
Changes occur in the actual or relative size of the parts already formed and in their functioning. No new features appear at this time.
By the end of the third lunar month, some internal organs are well enough developed to begin to function. Fetal heartbeat can be detected by about the fifteenth week.
By the end of the fifth lunar month, the different internal organs have assumed positions nearly like the ones they will have in the adult body.
Nerve cells, present from the third week, increase rapidly in number during the second, third, and fourth lunar months. Whether or not this rapid increase will continue and depend upon conditions within the mother's body such as malnutrition, which adversely affects nerve cell development - especially during the latter months of the prenatal period.
Fetal movements usually appear first between eighteen and twenty-two weeks and then increase rapidly up to the end of the ninth lunar month when they slow down because of crowding in the amniotic sac and pressure on the fetal brain as the fetus takes a head-down position in the pelvic region in preparation for birth. These fetal movements are of different kinds - rolling and kicking and short or quick movements.
By the end of the seventh lunar month, the fetus is well enough developed to survive, should it be born prematurely.
By the end of the eighth lunar month the fetal body is completely formed, though smaller than that of a normal, full-term infant.
At no other time during the life span are there more serious hazards to development or hazards of a more serious nature, than during the relatively short period before birth. These may be physical or psychological.
The zygote will die of starvation if it has too little yolk to keep it alive until it can lodge itself in the uterine wall or if it remains too long in the tube.
Implantation cannot occur if, as a result of glandular imbalance, the uterine walls are not prepared in time to receive the zygote.
If the zygote becomes attached to a small fibroid tissue in the uterine wall or to the wall of the Fallopian tube, it cannot get nourishment and will die.
Falls, emotional shocks, malnutrition, glandular disturbances, vitamin deficiency, and serious diseases such as pneumonia and diabetes, can cause the embryo to become dislodged from its place in the uterine wall, resulting in a miscarriage. Miscarriages that are due to unfavourable conditions in the prenatal environment are likely to occur between the tenth and eleventh week after conception.
Maternal malnutrition, vitamin and glandular deficiencies; excessive use of drugs, alcohol, and tobacco; and diseases, such as diabetes and German measles, interfere with normal development, especially that of the embryonic brain.
Miscarriages are always possible upto the fifth month of pregnancy; the most vulnerable time is when the woman's menstrual period would normally occur.
Fetuses which weigh less than 1 kg have less chance of surviving than heavier fetuses and a greater chance of developing malformations.
Maternal stress affects uterine contractions and is likely to lead to complications during birth.
Any of the unfavorable environmental conditions present during the period of the embryo will also affect the development of fetal features and retard the whole pattern of fetal development. Psychological Hazards -Like the physical hazards associated with the prenatal period, the psychological hazards can have persistent effects on the individual's development and can influence the postnatal environment and the treatment the child receives from significant people during the early formative years. The three important psychological hazards are traditional beliefs about prenatal development, maternal stress during the period and unfavourable attitude towards the unborn child on the part of people who will play significant roles in the child's life.
Traditional belief include-how one can predict the sex of an unborn child from heart-beat test or sliva test.
Twins were believed to be caused by evil spirits and thus were feared and rejected by the social group. Stress can be the result of fear, anger, grief, jealousy etc. Maternal stress can start from not wanting a child to any disturbance in the feelings and thought of the child unfavourable on others on the part of the father to be who blames his wife for being careless and make her feel guilty about not preventing the pregnancy or attitude toward children of multiple birth and many such unfavorable attitudes have far reaching influence on development.
The second and important stage in the life span is 'infancy'. This stage will deal with characteristics of infancy, adjustments, kinds of birth and activities.