Temperament describes the stable, early-appearing individual variations in behavioral dimensions including emotionality (crying, laughing, sulking), activity level, attention, sociability, and persistence. The classic theory of Thomas and Chess proposes 9 dimensions of temperament (Table 6-1). These characteristics lead to 3 common constellations: (1) the easy, highly adaptable child, who has regular biologic cycles; (2) the difficult child, who withdraws from new stimuli and is easily frustrated; and (3) the slow-to-warm-up child, who needs extra time to adapt to new circumstances. Various combinations of these clusters also occur. Temperament has long been described as biologic or “inherited,” largely based on parent reports (although confirmed by some independent observational studies) of twins. Monozygotic twins are rated by their parents as temperamentally similar more often than are dizygotic twins. Estimates of heritability suggest that genetic differences account for approximately 20-60% of the variability of temperament within a population. It had been presumed that the remaining 80-40% of the variance was environmentally influenced because genetic influences tended to be viewed as static. We now know that genes are dynamic, changing in the quantity and quality of their effects as a child ages and thus, like environment, may continue to change. Longitudinal twin studies of adult personality indicate that personality changes largely result from non-shared environmental influences, whereas stability of temperament appears to result from genetic factors. Although associations between specific genes and temperament have been noted (a 48-base pair repeat in exon 3 of DRD4 has been associated with novelty seeking), such associations require replication studies before they can be viewed as causative.

Table 6-1 TEMPERAMENTAL CHARACTERISTICS: DESCRIPTIONS AND EXAMPLES *

CHARACTERISTIC	DESCRIPTION	EXAMPLES^†
Activity level	Amount of gross motor movement	“She’s constantly on the move.” “He would rather sit still than run around.”
Rhythmicity	Regularity of biologic cycles	“He’s never hungry at the same time each day.” “You could set a watch by her nap.”
Approach and withdrawal	Initial response to new stimuli	“She rejects every new food at first.” “He sleeps well in any place.”
Adaptability	Ease of adaptation to novel stimulus	“Changes upset him.” “She adjusts to new people quickly.”
Threshold of responsiveness	Intensity of stimuli needed to evoke a response (e.g., touch, sound, light)	“He notices all the lumps in his food and objects to them.” “She will eat anything, wear anything, do anything.”
Intensity of reaction	Energy level of response	“She shouts when she is happy and wails when she is sad.” “He never cries much.”
Quality of mood	Usual disposition (e.g., pleasant, glum)	“He does not laugh much.” “It seems like she is always happy.”
Distractibility	How easily diverted from ongoing activity	“She is distracted at mealtime when other children are nearby.” “He doesn’t even hear me when he is playing.”
Attention span and persistence	How long a child pays attention and sticks with difficult tasks	“He goes from toy to toy every minute.” “She will keep at a puzzle until she has mastered it.”

* Based on Chess S, Thomas A: Temperament in clinical practice, New York, 1986, Guilford.

^† Typical statements of parents, reflecting the range for each characteristic from very little to very much.

The concept of temperament can help parents understand and accept the characteristics of their children without feeling responsible for having caused them. Children who have difficulty adjusting to change may have behavior problems when a new baby arrives or at the time of school entry. In addition, pointing out the child’s temperament may allow for adjustment in parenting styles. Behavioral and emotional problems may develop when the temperamental characteristics of children and parents are in conflict.

Psychologic Influences: Attachment and Contingency

The influence of the child-rearing environment dominates most current models of development. Infants in hospitals and orphanages, devoid of opportunities for attachment, have severe developmental deficits. Attachment refers to a biologically determined tendency of a young child to seek proximity to the parent during times of stress and also to the relationship that allows securely attached children to use their parents to re-establish a sense of well-being after a stressful experience. Insecure attachment may be predictive of later behavioral and learning problems.

At all stages of development, children progress optimally when they have adult caregivers who pay attention to their verbal and nonverbal cues and respond accordingly. In early infancy, such contingent responsiveness to signs of overarousal or underarousal helps maintain infants in a state of quiet alertness and fosters autonomic self-regulation. Contingent responses (reinforcement depending on the behavior of the other) to nonverbal gestures create the groundwork for the shared attention and reciprocity that are critical for later language and social development. Children learn best when new challenges are just slightly harder than what they have already mastered; a degree of difficulty dubbed the “zone of proximal development.” Psychologic forces, such as attention problems or mood disorders, will have profound effects on many aspects of an older child’s life.

Social Factors: Family Systems and the Ecologic Model

Contemporary models of child development recognize the critical importance of influences outside of the mother-child dyad. Fathers play critical roles, both in their direct relationships with their children and in supporting mothers. As traditional nuclear families become less dominant, the influence of other family members (grandparents, foster and adoptive parents, same-sex partners) becomes increasingly important. In addition, children are increasingly raised by unrelated caregivers while parents work or while they are in foster care.

Families function as systems, with internal and external boundaries, subsystems, roles, and rules for interaction. In families with rigidly defined parental subsystems, children may be denied any decision-making, exacerbating rebelliousness. In families with poorly defined parent-child boundaries, children may be required to take on responsibilities beyond their years, or may be recruited to play a spousal role.

Individuals within systems adopt implicit roles. For example, one child may be the troublemaker, whereas another is the negotiator and another is quiet. Birth order may have profound effects on personality development, through its influence on family roles and patterns of interaction. Families are also dynamic. Changes in one person’s behavior affect every other member of the system; roles shift until a new equilibrium is found. The birth of a new child, attainment of developmental milestones such as independent walking, the onset of nighttime fears, and the death of a grandparent are all changes that require renegotiation of roles within the family and have the potential for healthy adaptation or dysfunction.

The family system, in turn, functions within the larger systems of extended family, subculture, culture, and society. Bronfenbrenner’s ecologic model depicts these relationships as concentric circles, with the parent-child dyad at the center (with associated risks and protective factors) and the larger society at the periphery. Changes at any level are reflected in the levels above and below. The shift from an industrial economy to one based on service and information is an obvious example of societal change with profound effects on families and children.

Unifying Concepts: The Transactional Model, Risk, and Resilience

The transactional model proposes that a child’s status at any point in time is a function of the interaction between biologic and social influences. The influences are bidirectional: Biologic factors, such as temperament and health status, both affect the child-rearing environment and are affected by it. A premature infant may cry little and sleep for long periods; the infant’s depressed parent may welcome this good behavior, setting up a cycle that leads to poor nutrition and inadequate growth. The child’s failure to thrive may reinforce the parent’s sense of failure as a parent. At a later stage, impulsivity and inattention associated with early, prolonged undernutrition may lead to aggressive behavior. The cause of the aggression in this case is not the prematurity, the undernutrition, or the maternal depression, but the interaction of all these factors (Fig. 6-2). Conversely, children with biologic risk factors may nevertheless do well developmentally if the child-rearing environment is supportive. Premature infants with electroencephalographic evidence of neurologic immaturity may be at increased risk for cognitive delay. This risk may only be realized when the quality of parent-child interaction is poor. When parent-child interactions are optimal, prematurity carries a reduced risk of developmental disability.

Figure 6-2 Theoretical model of mutual influences on maternal depression and child adjustment.

(From Elgar FJ, McGrath PJ, Waschbusch DA, et al: Mutual influences on maternal depression and child adjustment problems, Clin Psychol Rev 24:441–459, 2004.)

Children growing up in poverty experience multiple levels of developmental risk: increased exposure to biologic risk factors, such as environmental lead and undernutrition, lack of stimulation in the home, and decreased access to interventional education and therapeutic experiences. As they respond by withdrawal or acting out, they further discourage positive stimulation from those around them. Children of adolescent mothers are also at risk. When early intervention programs provide timely, intensive, comprehensive, and prolonged services, at-risk children show marked and sustained upswings in their developmental trajectory. Early identification of children at developmental risk, along with early intervention to support parenting, is critically important.

An estimate of developmental risk can begin with a tally of risk factors, such as low income, limited parental education, and lack of neighborhood resources. There is a direct relationship between developmental outcome at age 13 yr and the number of social and family risk factors at age 4 yr (Fig. 6-3). Protective (resilience) factors must also be considered. These factors, like risk factors, may be either biologic (temperamental persistence, athletic talent) or social. The personal histories of children who overcome poverty often include at least one trusted adult (parent, grandparent, teacher) with whom the child has a special, supportive, close relationship.

Figure 6-3 Relationship between mean IQ scores at 13 yr (both raw and adjusted for covariation of mother’s IQ), as related to the number of risk factors. WISC-R, Wechstler Intelligence Scale-Revised.

(From Sameroff AJ, Seifer R, Baldwin A, et al: Stability of intelligence from preschool to adolescence; the influence of social and family risk factors, Child Dev 64:80–97, 1993.)

Developmental Domains and Theories of Emotion and Cognition

Child development can also be tracked by the child’s developmental progress in particular domains, such as gross motor, fine motor, social, emotional, language, and cognition. Within each of these categories are developmental lines or sequences of changes leading up to particular attainments. Developmental lines in the gross motor domain, leading from rolling to creeping to independent walking, are obvious. Others, such as the line leading to the development of conscience, are more subtle.

The concept of a developmental line implies that a child passes through successive stages. Several psychoanalytic theories are based on stages as qualitatively different epochs in the development of emotion and cognition (Table 6-2). In contrast, behavioral theories rely less on qualitative change and more on the gradual modification of behavior and accumulation of competence.

Table 6-2 CLASSIC STAGE THEORIES

Psychoanalytic Theories

At the core of Freudian theory is the idea of body-centered (or, broadly, “sexual”) drives. The focus of the drives shifts with maturation from oral satisfactions (sucking in the 1st yr of life), to anal sensations (holding on and letting go during the toddler years), oedipal drives (possessiveness toward a parent in the preschool years), and genital drives (in puberty and beyond) (see Table 6-2). At each stage, the child’s drive can potentially conflict with the rules of society. Infants may want to suck longer than the mother wants to nurse, or toddlers may decide that they like making a mess. The emotional health of both the child and the adult depends on adequate resolution of these conflicts. Freud saw middle childhood as a period of latency, when the sexual drive is redirected (sublimated) to the achievement of social or external goals.

Freudian ideas have been challenged. Few believe that the manner of toilet training permanently shapes personality, and middle childhood is no longer seen as conflict-free. Moreover, the effectiveness of psychoanalytic therapy has been difficult to demonstrate empirically. Nonetheless, the Freudian legacy includes concepts that are central to an understanding of emotional development: the importance of a child’s inner life and sexuality, the normative existence of emotional conflict during childhood, and the possibility that emotional disturbance can have early roots.

Erikson’s chief contribution was to recast Freud’s stages in terms of the emerging personality (see Table 6-2). The child’s sense of basic trust develops through the successful negotiation of infantile needs, corresponding to Freud’s oral period. As children progress through these psychosocial stages, different issues become salient. Thus, it is predictable that a toddler will be preoccupied with establishing a sense of autonomy, whereas a late adolescent may be more focused on establishing meaningful relationships and an occupational identity. Erikson recognized that these stages arise in the context of Western European societal expectations; in other cultures, the salient issues may be quite different.

Erikson’s work calls attention to the intrapersonal challenges facing children at different ages in a way that facilitates professional intervention. Knowing that the salient issue for school-aged children is industry vs inferiority, pediatricians know to inquire about a child’s experiences of mastery and failure and (if necessary) suggest ways to ensure adequate successes.

Cognitive Theories

Cognitive development is best understood through the work of Piaget. A central tenet of Piaget’s work is that cognition changes in quality, not just quantity (see Table 6-2). During the sensorimotor stage, an infant’s thinking is tied to immediate sensations and a child’s ability to manipulate objects. The concept of “in” is embodied in a child’s act of putting a block into a cup. With the arrival of language, the nature of thinking changes dramatically; symbols increasingly take the place of objects and actions. Piaget described how children actively construct knowledge for themselves through the linked processes of assimilation (taking in new experiences according to existing schemata) and accommodation (creating new patterns of understanding to adapt to new information). In this way, children are continually and actively reorganizing cognitive processes.

Piaget’s basic concepts have held up well. Challenges have included questions about the timing of various stages and the extent to which context may affect conclusions about cognitive stage. Children’s understanding of cause and effect may be considerably more advanced in the context of sibling relationships than in the manipulation and perception of inanimate objects. In many children, logical thinking appears well before puberty, the age postulated by Piaget. Of undeniable importance are Piaget’s focus on cognition as a subject of empirical study, the universality of the progression of cognitive stages, and the image of a child as actively and creatively interpreting the world.

Piaget’s work is of special importance to pediatricians for 3 reasons: (1) It helps make sense of many puzzling behaviors of infancy, such as the common exacerbation of sleep problems at 9 and 18 mo of age. (2) Piaget’s observations often lend themselves to quick replication in the office, with little special equipment. (3) Open-ended questioning, based on Piaget’s work, can provide insights into children’s understanding of illness and hospitalization.

Based on cognitive development, Kohlberg developed a theory of moral development in 6 stages from early childhood through adulthood. Preschoolers’ earliest sense of right and wrong is egocentric, motivated by externally applied controls. In later stages, children perceive equality, fairness, and reciprocity in their understanding of interpersonal interactions through perspective-taking. Most youth will reach stage 4, conventional morality, by mid to late adolescence. The basic theory has been modified to distinguish morality from social conventions. Whereas moral thinking considers interpersonal interactions, justice, and human welfare, social conventions are the agreed-on standards of behavior particular to a social or cultural group. Within each stage of development, children are guided by the basic precepts of moral behavior, but also may take into account local standards, such as dress code, classroom behavior, and dating expectations.

Behavioral Theory

This theoretical perspective distinguishes itself by its lack of concern with a child’s inner experience. Its sole focus is on observable behaviors and measurable factors that either increase or decrease the frequency with which these behaviors occur. No stages are implied; children, adults, and indeed animals all respond in the same way. In its simplest form, the behaviorist orientation asserts that behaviors that are positively reinforced occur more frequently; behaviors that are negatively reinforced or ignored occur less frequently. The strengths of this position are its simplicity, wide applicability, and conduciveness to scientific verification. A behavioral approach lends itself to interventions for various common problems, such as temper tantrums and aggressive preschool behavior, in which behaviors are broken down into discrete units. In cognitively limited children and children with autism spectrum disorders, behavioral interventions using applied behavior analysis (ABA) approaches have demonstrated their ability to teach new, complex behaviors. ABA has been particularly useful in the treatment of early diagnosed autism (Chapter 28.1). However, in cases in which misbehavior is symptomatic of an underlying emotional, perceptual, or family problem, an exclusive reliance on behavior therapy risks leaving the cause untreated. Behavioral approaches can be taught to parents to apply at home.

Theories Commonly Employed in Behavioral Interventions

During the past few decades an increasing number of programs (within and outside of the physician’s office) designed to influence behavior have been based on theoretical models of behavior. Some of these models are based on behavioral or cognitive theory or in cases have attributes of both. The most commonly employed models are the Health Belief Model, Theory of Reasoned Action, Theory of Planned Behavior, Social Cognitive Theory, and the Transtheoretical Model, also known as Stages of Change Theory. Pediatricians should be aware of these models; similarities and differences between these models are shown in Table 6-3. Motivational interviewing is less a theory of behavior and more a technique to bring about behavior change. The goal in using the technique is to enhance an individual’s motivation to change behavior by exploring and removing ambivalence. This may be practiced by an individual practitioner and is being taught in some pediatric residency programs. Motivational interviewing emphasizes the importance of the therapist (pediatrician) understanding the client’s perspective and displaying unconditional support. The therapist is a partner rather than an authority figure and recognizes that ultimately the patient has control over his or her choices.

Statistics Used in Describing Growth and Development (Chapters 13 and 14)

In everyday use, the term normal is synonymous with healthy. In a statistical sense, normal means that a set of values generates a normal (bell-shaped or gaussian) distribution. This is the case with anthropometric quantities, such as height and weight, and with many developmental milestones, such as the age of independent standing. For a normally distributed measurement, a histogram with the quantity (height, age) on the x-axis and the frequency (the number of children of that height, or the number who stand on their own at that age) on the y-axis generates a bell-shaped curve. In an ideal bell-shaped curve, the peak corresponds to the arithmetic mean (average) of the sample and to the median and the mode as well. The median is the value above and below which 50% of the observations lie; the mode is the value having the highest number of observations. Distributions are termed skewed if the mean, median, and mode are not the same number.

The extent to which observed values cluster near the mean determines the width of the bell and can be described mathematically by the standard deviation (SD). In the ideal normal curve, a range of values extending from 1 SD below the mean to 1 SD above the mean includes approximately 68% of the values, and each “tail” above and below that range contains 16% of the values. A range encompassing ±2 SD includes 95% of the values (with the upper and lower tails each comprising approximately 2.5% of the values), and ±3 SD encompasses 99.7% of the values (Table 6-4 and Fig. 6-4).

Table 6-4 RELATIONSHIP BETWEEN SD AND NORMAL RANGE FOR NORMALLY DISTRIBUTED QUANTITIES

Figure 6-4 Relationship between percentile lines on the growth curve and frequency distributions of height at different ages.

For any single measurement, its distance away from the mean can be expressed in terms of the number of SDs (also called a z score); one can then consult a table of the normal distribution to find out what percentage of measurements fall within that distance from the mean. Software to convert anthropometric data into z scores for epidemiologic purposes is available. A measurement that falls “outside the normal range”—arbitrarily defined as 2, or sometimes 3, SDs on either side of the mean—is atypical, but not necessarily indicative of illness. The further a measurement (say, height, weight, or IQ) falls from the mean, the greater the probability that it represents not simply normal variation, but rather a different, potentially pathologic, condition.

Another way of relating an individual to a group uses percentiles. The percentile is the percentage of individuals in the group who have achieved a certain measured quantity (e.g., a height of 95 cm) or a developmental milestone (e.g., walking independently). For anthropometric data, the percentile cutoffs can be calculated from the mean and SD. The 5th, 10th, and 25th percentiles correspond to −1.65 SD, −1.3 SD, and −0.7 SD, respectively. Figure 6-4 demonstrates how frequency distributions of a particular parameter (height) at different ages relate to the percentile lines on the growth curve.

Bibliography

Arkowitz H, Westra HA. Introduction to the special series on motivational interviewing and psychotherapy. J Clin Psychol. 2009;65:1149-1155.

Bandura A. Social learning theory. Englewood Cliffs, NJ: Prentice-Hall; 1977. 1977, pp 2–13

Bronfenbrenner U. The ecology of human development. Cambridge, MA: Harvard University Press; 1979.

Carey WB. Teaching parents about infant temperament. Pediatrics. 1998;102:1311-1316.

Duncan GJ, Magnuson KA. Can family socioeconomic resources account for racial and ethnic test score gaps? Future Child. 2005;15:35-54.

Evans GW. The environment of childhood poverty. Am Psychol. 2004;59:77-92.

Frankowski BL, Leader IC, Duncan PM. Strength-based interviewing. Adolesc Med State Art Rev. 2009;20:22-40. vii–viii

Johnston MV. Plasticity in the developing brain: implications for rehabilitation. Dev Disabil Res Rev. 2009;15:94-101.

Keverne EB. Understanding well-being in the evolutionary context of brain development. Phil Trans R Soc Lond B Biol Soc. 2004;359:1349-1358.

Noar SM, Zimmerman RS. Health Behavior Theory and cumulative knowledge regarding health behaviors: are we moving in the right direction? Health Educ Res. 2005;20:275-290.

Saudino KJ. Behavioral genetics and child temperament. J Dev Behav Pediatr. 2005;26:214-223.

Shonkoff J, Phillips D. National Research Council and Institute of Medicine: From Neurons to Neighborhoods: The Science of Early Childhood Development. Washington, DC: National Academy Press; 2000.

Walker SP, Wachs TD, Gardner JM, et al. Child development: risk factors for adverse outcomes in developing countries. Lancet. 2007;369:145-157.

6.1 Assessment of Fetal Growth and Development

Susan Feigelman

The most dramatic events in growth and development occur before birth and involve the transformation of a fertilized egg into an embryo and a fetus, the elaboration of the nervous system, and the emergence of behavior in utero. The psychologic changes occurring in the parents during the gestation profoundly impact the lives of all members of the family. The developing fetus is affected by such social and environmental influences as maternal undernutrition; alcohol, cigarette, and drug use (both legal and illicit); and psychologic trauma. The complex interplay between these forces and the somatic and neurologic transformations occurring in the fetus influence growth and behavior at birth, through infancy, and potentially throughout the individual’s life.

Somatic Development

Embryonic Period

Milestones of prenatal development are presented in Table 6-5. By 6 days postconceptual age, as implantation begins, the embryo consists of a spherical mass of cells with a central cavity (the blastocyst). By 2 wk, implantation is complete and the uteroplacental circulation has begun; the embryo has 2 distinct layers, endoderm and ectoderm, and the amnion has begun to form. By 3 wk, the 3rd primary germ layer (mesoderm) has appeared, along with a primitive neural tube and blood vessels. Paired heart tubes have begun to pump.

Table 6-5 MILESTONES OF PRENATAL DEVELOPMENT

WK	DEVELOPMENTAL EVENTS
1	Fertilization and implantation; beginning of embryonic period
2	Endoderm and ectoderm appear (bilaminar embryo)
3	First missed menstrual period; mesoderm appears (trilaminar embryo); somites begin to form
4	Neural folds fuse; folding of embryo into human-like shape; arm and leg buds appear; crown-rump length 4-5 mm
5	Lens placodes, primitive mouth, digital rays on hands
6	Primitive nose, philtrum, primary palate
7	Eyelids begin; crown-rump length 2 cm
8	Ovaries and testes distinguishable
9	Fetal period begins; crown-rump length 5 cm; weight 8 g
12	External genitals distinguishable
20	Usual lower limit of viability; weight 460 g; length 19 cm
25	Third trimester begins; weight 900 g; length 24 cm
28	Eyes open; fetus turns head down; weight 1,000-1,300 g
38	Term

During wk 4-8, lateral folding of the embryologic plate, followed by growth at the cranial and caudal ends and the budding of arms and legs, produces a human-like shape. Precursors of skeletal muscle and vertebrae (somites) appear, along with the branchial arches that will form the mandible, maxilla, palate, external ear, and other head and neck structures. Lens placodes appear, marking the site of future eyes; the brain grows rapidly. By the end of wk 8, as the embryonic period closes, the rudiments of all major organ systems have developed; the crown-rump length is 3 cm.

Fetal Period

From the 9th wk on (fetal period), somatic changes consist of rapid body growth as well as differentiation of tissues, organs, and organ systems. Changes in body proportion are depicted in Figure 6-5. By wk 10, the face is recognizably human. The midgut returns to the abdomen from the umbilical cord, rotating counterclockwise to bring the stomach, small intestine, and large intestine into their normal positions. By wk 12, the gender of the external genitals becomes clearly distinguishable. Lung development proceeds, with the budding of bronchi, bronchioles, and successively smaller divisions. By wk 20-24, primitive alveoli have formed and surfactant production has begun; before that time, the absence of alveoli renders the lungs useless as organs of gas exchange.

Figure 6-5 Changes in body proportions from the 2nd fetal mo to adulthood.

(From Robbins WJ, Brody S, Hogan AG, et al: Growth, New Haven, CT, 1928, Yale University Press.)

During the 3rd trimester, weight triples and length doubles as body stores of protein, fat, iron, and calcium increase.

Neurologic Development

During the 3rd wk, a neural plate appears on the ectodermal surface of the trilaminar embryo. Infolding produces a neural tube that will become the central nervous system (CNS) and a neural crest that will become the peripheral nervous system. Neuroectodermal cells differentiate into neurons, astrocytes, oligodendrocytes, and ependymal cells, whereas microglial cells are derived from mesoderm. By the 5th wk, the 3 main subdivisions of forebrain, midbrain, and hindbrain are evident. The dorsal and ventral horns of the spinal cord have begun to form, along with the peripheral motor and sensory nerves. Myelinization begins at midgestation and continues through the 1st yr of life.

By the end of the embryonic period (wk 8), the gross structure of the nervous system has been established. On a cellular level, neurons migrate outward to form the 6 cortical layers. Migration is complete by the 6th mo, but differentiation continues. Axons and dendrites form synaptic connections at a rapid pace, making the CNS vulnerable to teratogenic or hypoxic influences throughout gestation. Rates of increase in DNA (a marker of cell number), overall brain weight, and cholesterol (a marker of myelinization) are shown in Figure 6-6. The prenatal and postnatal peaks of DNA probably represent rapid growth of neurons and glia, respectively. By the time of birth, the structure of the brain is complete. Synapses will be pruned back substantially and new connections will be made, largely as a result of experience.

Figure 6-6 Velocity curves of the various components of human brain growth. Solid line with two peaks, DNA; dashed line, brain weight; solid line with a single peak, cholesterol.

(From Brasel JA, Gruen RK. In Falkner F, Tanner JM, editors: Human growth: a comprehensive treatise, New York, 1986, Plenum Press, pp 78–95.)

Behavioral Development

No behavioral evidence of neural function is detectable until the 3rd month. Reflexive responses to tactile stimulation develop in a craniocaudal sequence. By wk 13-14, breathing and swallowing motions appear. The grasp reflex appears at 17 wk and is well developed by 27 wk. Eye opening occurs around 26-28 wk. By midgestation, the full range of neonatal movements can be observed.

During the 3rd trimester, fetuses respond to external stimuli with heart rate elevation and body movements (Chapter 90). As with infants in the postnatal period, reactivity to auditory (vibroacoustic) and visual (bright light) stimuli vary depending on their behavioral state, which can be characterized as quiet sleep, active sleep, or awake. Individual differences in the level of fetal activity are commonly noted by mothers and have been observed ultrasonographically. Fetal behavior is affected by maternal medications and diet, increasing after ingestion of caffeine. Behavior may be entrained to the mother’s diurnal rhythms: asleep during the day, active at night.

Fetal movement increases in response to a sudden auditory tone, but decreases after several repetitions. This demonstrates habituation, a basic form of learning in which repeated stimulation results in a response decrement. If the tone changes in pitch, the movement increases again, evidence that the fetus distinguishes between a familiar, repeated tone and a novel one. Habituation improves in older fetuses, and decreases in neurologically impaired or physically stressed fetuses. Similar responses to visual and tactile stimuli have been observed.

Psychologic Changes in Parents

Many psychologic changes occur during pregnancy. An unplanned pregnancy may be met with anger, denial, or depression. Ambivalent feelings are the norm, whether or not the pregnancy was planned. Elation at the thought of producing a baby and the wish to be the perfect parent compete with fears of inadequacy and of the lifestyle changes that mothering will impose. Old conflicts may resurface as a woman psychologically identifies with her own mother and with herself as a child. The father-to-be faces similar mixed feelings, and problems in the parental relationship may intensify.

Tangible evidence that a fetus exists as a separate being, whether as a result of ultrasonic visualization or awareness of fetal movements (at approximately 20 wk), often heightens a woman’s feelings, both positive and negative. Parents worry about the fetus’s healthy development and mentally rehearse what they will do if the child is malformed. Reassurances based on ultrasound examinations or amniocentesis may not completely allay these fears. Toward the end of pregnancy, a woman becomes aware of patterns of fetal activity and reactivity and begins to ascribe to her fetus an individual personality and an ability to survive independently. Appreciation of the psychologic vulnerability of the expectant parents and of the powerful contribution of fetal behavior facilitates supportive clinical intervention.

Threats to Fetal Development

Mortality and morbidity are highest during the prenatal period (Chapter 87). An estimated 50% of all pregnancies end in spontaneous abortion, including approximately 10-25% of all clinically recognized pregnancies. The vast majority occur in the 1st trimester. Some occur as a result of chromosomal or other abnormalities.

The association between an inadequate nutrient supply to the fetus with low birthweight has been recognized for decades; this adaptation on the part of the fetus will the inadequate supply presumably increases the likelihood that the fetus will survive until birth. Also recognized for decades is the fact that for any potential fetal insult, the extent and nature of its effects are determined by characteristics of the host as well as the dose and timing of the exposure. Inherited differences in the metabolism of ethanol may predispose certain individuals or groups to fetal alcohol syndrome. Organ systems are most vulnerable during periods of maximum growth and differentiation, generally during the 1st trimester (organogenesis). Figure 6-7 depicts sensitive periods during gestation for various organ systems. (See also http://www.criticalwindows.com/go_display.php for a more detailed listing of critical periods and specific developmental abnormalities.)