Development of a Normal Child
Robert H. Duckman
David A. Maze
A very important component of a pediatric patient’s case history is the child’s developmental history. Optometric students and clinicians should always ask the parents about developmental patterns of the child. A comprehensive knowledge of this process is crucial in rendering appropriate optometric care to young patients. Understanding normal developmental sequences can help with clinical decision making (including appropriate referrals) for a slowly developing child.
The study of child development focuses on changes that involve behavioral reorganizations and qualitative differences from one age to the next (1). Many theories have been perpetuated over many decades to explain motor development, cognitive development, and emotional development. All of the theories state that changes taking place will follow a lawful and logical sequence; they are cumulative and become more complex as the child ages (1,2).
The term normal development pertains to typical changes that are shared by almost all children over time (3). These changes may not take place at the same time in all children, but most researchers recognize that there are average ages at which various milestones are reached.
Two early views have been influential in the study of child development. The English philosopher, John Locke, and French philosopher, Jean Jacques Rousseau, formulated their theories in the 17th and 18th, centuries respectively. Locke felt that children developed into what they are as a function of their environment. Rousseau thought that human development unfolds naturally as long as society allows it. The latter theory appealed to child development researchers who stressed a general developmental pattern that nearly all children share. Perhaps one of the best known of these researchers was Arnold Gesell.
Arnold Gesell conducted research in the 1920s and 1930s at Yale University. His studiesc focused on children’s physical development and acquisition of motor skills. Gesell felt that patterns unfold naturally with maturation. Gesell studied and recorded changes in children from birth to 10 years of age. He felt that all children pass through universal stages in life and that motor development is the foundation for all mental life (4).
Out of the many researched child development theories, the two major theories involve cognitive development. The information-processing theory views the human brain as a computer. Developmentalists who take this perspective are concerned with changes in a maturing child’s memory and problem-solving skills (5,6). One of the most well-known human development theorists, Jean Piaget, developed his
theory based on normative cognitive development. He felt that children not only know less, but also have a different qualitative knowledge than adults. Piaget’s theories, although not accepted by everyone, are still the most embraced and researched philosophies on child development.
theory based on normative cognitive development. He felt that children not only know less, but also have a different qualitative knowledge than adults. Piaget’s theories, although not accepted by everyone, are still the most embraced and researched philosophies on child development.
Theories that pertain more to social and emotional rather than cognitive development are social learning theory, psychoanalytic theory, and Bowlby’s adaptational theory (3). Social learning theory views development as a gradual and cumulative process focusing on behavior. That is, children learn by understanding the consequences of their own actions and learning from the consequences of others’ behavior. Freud’s psychoanalytic theory purports that abnormal behavior results from an inadequate expression of innate drives. Erickson broadened this to a psychosocial theory. Bowlby’s adaptational theory integrates social, emotional, and cognitive aspects of development.
Of the numerous theories relating to child development, each focuses on different aspects of that development. Currently there is no universally accepted theory in the field of development psychology. Findings in this area can sometimes be interpreted in different ways. Most theories fall between two beliefs—either an infant is naive at birth and learns from the environment or the brain develops in a predetermined, preprogrammed manner (7). As a clinician trying to understand normal child development, this can be a confusing concept. However, considering development to be a combination of “pre-wiring” and environmental learning may be helpful in understanding normal child development.
Normal Pregnancy
One important group of questions to ask while evaluating a pediatric patient’s optometric case history concerns the pregnancy and birth process. While normal pregnancy and birth generally lead to normal development, abnormal pregnancy and birth often lead to abnormal development. From the moment of conception all the way through the delivery process many events occur that can have a large impact on the development of a child.
Conception
Conception takes place when a sperm penetrates the woman’s egg cell, or ovum. For this to happen, a series of events must take place. The egg cell will ripen in a woman’s ovary in about 28 days. When this ovum is ready for fertilization, it is released from the ovary to the fallopian tube. The egg passes through the fallopian tube down to the uterus. This passage takes place over several days, and the process is called ovulation. If the ovum is not penetrated by a sperm cell within the first day, it will disintegrate when it reaches the uterus. If, however, sexual intercourse takes place at the proper time, the egg meets potentially millions of sperm. When one of these sperm penetrates the ovum, a single-celled organism called a zygote is created, and conception has taken place (8). If two eggs are fertilized by two separate sperm, the result is dizygotic, or fraternal, twins. If, however, a single fertilized egg splits into two separate units early on, monozygotic, or identical, twins result.
Prenatal Development
Germinal Period: Conception Through Week 2
The germinal period begins the moment after conception. The zygote remains a single cell and pushes its way down the fallopian tubes. The process of mitosis, or cell division, takes place and the parent cell divides into two. The chromosomes in the original cell duplicate themselves. In a normal zygote, 46 chromosomes should be present: 23 from the sperm and 23 from the egg.
These cells continue to divide until the cells become a clustered, hollow, ball-like structure called a blastocyst. Usually around the sixth day, the blastocyst makes contact with the wall of the uterus. The lining has already become rich with blood in order to nourish the egg. The end of this stage is usually about 14 days, and the blastocyst becomes fully embedded in the uterine wall (8).
Embryonic Period: Weeks 3 Through 8
At weeks 3 through 8, the zygote becomes firmly implanted into the uterine wall, and becomes known as the embryo. This is a time of rapid
cell division and differentiation. It is at this time that the process called organogenesis (when cells develop into organs and body structures) takes place (8).
cell division and differentiation. It is at this time that the process called organogenesis (when cells develop into organs and body structures) takes place (8).
The embryo has an intricate support system that is composed of three major parts: the placenta, the umbilical cord, and the amniotic sac. The placenta is tissue that forms from uterine cells and part of the blastocyst. Blood vessels are linked from the placenta to the embryo by the umbilical cord. Nutrients, oxygen, waste products, and carbon dioxide are transferred to and away from the embryo by these blood vessels. The transfer of these materials occurs through cell membranes in the placenta with the uterine lining. This creates two separate blood supplies; the mother’s blood supply is separate from that of the embryo. Oxygen, carbon monoxide, and other small molecules can pass through the cell membranes, but blood cells cannot because they are too large. The membranes offer some protection against large molecules (e.g., most bacteria). They do not offer protection against smaller molecules such as viruses, alcohol, or many other chemicals.
The fluid-filled sac surrounding the embryo is called the amniotic sac. This sac provides a closed, protective environment for the embryo to develop. By acting as a cushion, it prevents harm or damage from bumping and shaking. This sac also acts to minimize any temperature changes when the mother is exposed to warmer and colder environments.
During the third week of this process, the first week of the embryonic period, the organism becomes oval with an indentation. The indentation will become the mouth and digestive tract. At the end of this week, the cells have differentiated into three major tissue types: endoderm, mesoderm, and ectoderm. The endoderm will develop into internal organs such as the stomach, liver, lungs, and so on. The mesoderm will become muscles, skeleton, and blood. The ectoderm will form the sensory organs, including the central nervous system and the skin.
Embryonic induction is a process of tissue interaction that shapes various organs and parts of the body (9). An example of this is when the lens forms based on the interaction of the ectoderm with the mesoderm.
By the end of the third week, the central nervous system has started to form and the eyes can be seen. In the fourth week, the heart and the digestive tract start to appear. By the end of the embryonic period, the fingers, toes, and bones are developing. This time period is very important as the critical period for organ development and differentiation takes place (8). The unborn child is vulnerable at this stage, but the mother may not realize that she is pregnant at this time. It becomes important for women to take care of their health if pregnancy is suspected because substance abuse or improper nutrition can lead to embryo damage.
The Fetal Period: Week 9 to Birth
The fetal period is an important one in which organs are now refined (8). This is when the skin becomes developed; the eyebrows and eyelashes grow; and, in the seventh month, the testes in males usually descend into the scrotum. The fetus grows in length dramatically from about 1 inch at 8 weeks to 12 inches at 24 weeks. The weight of the organism increases from 1 ounce at 12 weeks to 3 pounds at 28 weeks (1). The refinement and growth during this time frame becomes very important.
During this stage, the fetus becomes responsive to stimuli. After 10 weeks, the fetus flexes if any part of its body parts is touched. At about 18 weeks, the response given to body part stimulation becomes very specific. For example, touching the foot will produce a leg withdrawal at this time. At 7 months of age, the fetus may suck its thumb or hand. The eyes are now able to open and close because the lids have separated (8).
Birth
Normal Birth
The normal duration of gestation is 40 weeks. Infants have a good chance of survival if born in the seventh month and later (9). The fetus moves into a head-down position as it prepares for its journey down the birth canal. (Any posture other than this will cause birth complications and put the child at risk.) As the fetus changes position, the uterus responds by contracting; this process helps move the infant along.
There are three stages of labor. The first stage involves regular contractions that are
15 to 20 minutes apart. They become more frequent and stronger as labor progresses. The second stage is the crowning of the infant’s head. The head pushes its way from the cervix into the vagina. The contractions at this stage are much closer together—usually 1 minute apart. The final stage begins when the baby is born. The uterus continues to contract after the baby is delivered; this is so the placenta and other membranes can be expunged from the mother.
15 to 20 minutes apart. They become more frequent and stronger as labor progresses. The second stage is the crowning of the infant’s head. The head pushes its way from the cervix into the vagina. The contractions at this stage are much closer together—usually 1 minute apart. The final stage begins when the baby is born. The uterus continues to contract after the baby is delivered; this is so the placenta and other membranes can be expunged from the mother.
Table 24.1 Apgar Scores | ||||||||||||||||||||||||||||
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After the birth, it is common practice to evaluate the condition of the infant. Virginia Apgar created a system by which the baby can be assessed shortly after birth. The Apgar score is determined by rating the muscle tone, heart rate, reflexes, respiration, and color, each on a scale of 0 to 2. The Apgar scores are routinely assessed at 1 minute and at 5 minutes after birth (Table 24.1) (10). If an infant receives a score of 7 at the 5-minute scoring, the infant is considered to not be at risk. Lower scores usually indicate immediate medical attention is needed. Most infants score 7 or higher (11), with the maximal score being 10.
Average birth weight is 7.5 lb (∼3400 g), and the average length is 18 in (45.7 cm). The average newborn’s skull has become distorted after childbirth. The infant is usually bald, except possible thin hair in areas such as the neck, ears, and back. The infant’s breathing pattern is sporadic and filled with a fluidlike sound (9). Most newborns are unable to physically regulate body temperature because sweat glands are not developed nor is the ability to shiver. The newborn can have a striking appearance and is a very delicate entity.
Abnormal Birth
With advances in technology, viability of the fetus in premature births, even premature babies with extremely low birthweights, is becoming increasingly more likely (12). More than half of babies born after just 24 weeks of gestation can survive. Any infant born before 35 weeks is considered premature. Classification of low birthweight (LBW), 2500 to 1500 g (5.5 to 3.3 lb), very low birthweight (VLBW), 1499 to 1000 g (3.4 to 2.2 lb), and extremely low birthweight (ELBW), less than 1000 g (<2.2 lb), often accurately reflects how at risk the child is for developmental anomalies. The lower the birthweight, the greater the risk for developmental delays or disabilities in the premature baby (13). If an infant weighs less than 700 g (1.5 lb), it has a very low chance for survival. These infants often have a high incidence of neurologic problems, lung ailments, and other physical problems when they do survive.
Caesarean section deliveries are performed when significant fetal distress is encountered during the delivery process. When a vaginal delivery is not perceived as going well, or if an abnormal heart rate is detected, a caesarean section birth may be elected. No evidence exists which indicates that a caesarean section delivery increases mortality in infants or even damages the nervous system (3). Frequently, for a host of different reasons, the obstetrician will
opt for a caesarean section ahead of time and the delivery will be planned for a specific date.
opt for a caesarean section ahead of time and the delivery will be planned for a specific date.
Reflexes
Infant reflexes disappear as the baby grows older. Most of these built-in reactions should not persist into childhood. Reflexes can be broken down into survival reflexes and nonsurvival reflexes. An example of a survival reflex is the sucking reflex: When an object is inserted into the child’s mouth, the child will begin sucking. This reflex turns into a voluntary one after about 2 months. This is important biologically because if a nipple is presented to the infant, the infant must instinctively begin to feed. Another survival reflex is that of the rooting reflex. If an infant’s cheek is lightly stroked, the child will turn its head toward the cheek and open its mouth.
Reflexes may also be present that have no survival value. One such example is the Babinski reflex, in which the infant will fan the toes outward if the foot is stroked near the heel. This reflex should disappear by the age of 1 year. The grasping reflex is also a nonsurvival reflex. The infant will curl the fingers when pressure is placed on its palm. This can weaken by 3 months, but after this point the infant may develop a voluntary grasp (14).
Reflexes are seen as lower brain center activities (15). Because voluntary activities require higher brain center function, the transfer of reflexes to voluntary action may be related to the development of cerebral cortex neurons (15). The control from primitive reflexes to voluntary muscle control is attained through myelinization of the cerebral cortex. (16).
Motor Development
Physical growth is important for normal motor development. Two areas important to motor control in young children are large, gross muscle control and small, or fine, muscle control. For a child to develop motor abilities, it becomes important for muscles to develop. Large muscles develop before small muscles develop.
Infant motor control can be limited by physical development. Physical development should be rapid within the first year (1,2). By 2 months, the reflexes begin to disappear. The baby at this time can move his or her entire body, begin to raise the head while lying on the abdomen, and may begin to hold the head up for a few moments while sitting up.
By 3 months, the primitive reflexes should have disappeared. During this time period, when the infant’s reflexes disappear and voluntary control is gained, the baby may not move arms and legs as much. Around this time, the baby can raise the head and can hold it up in the sitting position. When supporting the self on forearms while lying on the abdomen, the infant can coordinate arm and leg movements on both sides. At 3 months, the grasp reflex may also have disappeared. The infant, however, is not yet able to pick things up.
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