Prenatal Developmentand the Newborn Period How Children Develop (3rd ed.) Siegler, DeLoache & Eisenberg Slides have been adapted. Chapter 2
Overview: Major Topics • I. Prenatal Development • II. The Birth Experience • III. The Newborn Infant
Guiding Questions What changes occur during prenatal development? How does the environment contribute to prenatal development? How does the developing child’s behavior contribute to its own development? Can learning occur during the prenatal period? What is daily life like for the newborn? What special risks threaten the developing newborn?
Changing Ideas Over Time Aristotle rejected the prevailing idea that the individual was preformed at the start of life in favor of epigenesis, the idea that there is an emergence of new structures and functions during development.
The Reproductive Process • An egg is launched from one of the woman’s ovaries into the fallopian tube. • If sexual intercourse takes place near the time the egg is released, then conception will be possible.
Conception • Results from the union of two gametes, the egg and the sperm • Gametes are produced through a specialized cell division, which results in each gamete’s having only half the genetic material of all other normal cells in the body. • Population sex differences begin at conception. More males are conceived, but males are more vulnerable after this point.
The Zygote • After conception, the fertilized egg, or zygote, has a full complement of human genetic material, half from each parent.
Processes Occurring During Prenatal Development • These processes transform a zygote into an embryo and then into a fetus. • Cell divisionresults in the proliferation of cells. • Cell migrationis the movement of cells from their point of origin to somewhere else in the embryo. • Cell differentiationtransforms the embryo’s unspecialized stem cells into different types of cells. • Apoptosis, genetically programmed cell death, also enables prenatal development.
Early Development • By the 4th day after conception, the zygote arranges itself into a hollow sphere of cells with a bulge of cells, the inner cell mass, on one side. • The inner cell mass eventually forms into the embryo.
The Embryo • After implantation, the inner cell mass becomes the embryo and the rest of the cells develop into its support system. • The neural tube is a U-shaped groove formed from the top layer of differentiated cells in the embryo. • It eventually becomes the brain and the spinal cord.
Teratogens • Environmental agents that have the potential to cause harm during prenatal development. • Timing is a crucial factor in the severity of the effects of potentially harmful agents. • Many agents cause damage only if exposure occurs during a sensitive period in development.
Most teratogens show a dose-response relation. • Increases in exposure to potential teratogens are associated with greater probabilities of fetal defects and with more severe problems. • Individual differences also influence the effects of teratogens.
Teratogens • Identifying teratogens is made difficult by the existence of sleeper effects in which the impact of a given agent may not be apparent for many years. • Teratogens include legal as well as illegal substances...
Legal Drugs: Cigarettes • Cigarette smoking during pregnancy is linked to retarded growth and low birth weight. • Cigarette smoking has also been linked to SIDS (sudden infant death syndrome), although the ultimate causes of SIDS are still unknown. • Parents can reduce the risk of SIDS by not smoking, putting babies to sleep on their backs rather than on their stomachs, using firm mattresses and no pillows as bedding for infants, and avoiding wrapping infants in lots of blankets or clothing.
Legal Drugs: Alchohol • Maternal alcoholism can lead to fetal alcohol spectrum disorder (FASD), which is associated with mental retardation, facial deformity, and other problems.
Illegal Drugs • Approximately 4% of pregnant women in the U.S. use illicit drugs. • Marijuana is suspected of affecting memory, learning, and visual skills after birth. • Cocaine-exposed children have reported cognitive and social deficits.
Environmental Pollutants • Toxic metals, synthetic hormones, and various ingredients of plastics, pesticides, and herbicides can be teratogenic. • PCBs (polycholorinated biphenyls) have been associated with small head size as newborns and slightly lower IQ scores as long as 11 years later.
Occupational Hazards • Many women have jobs that bring them into contact with potentially hazardous elements (e.g., automobile exhaust, pesticides, chemicals, noise pollution).
Maternal Factors • The age, nutrition, disease, and emotional state of the mother have an impact on prenatal development • Infants born to girls 15 years or younger are three to four times more likely to die before their first birthday than are those whose mothers 23-29 years of age. • An inadequate supply of specific nutrients or vitamins such as folic acid can have dramatic consequences. • A variety of diseases including sexually transmitted diseases present hazards to the fetus. • A woman’s emotional state can affect her fetus.
Protecting the Fetus • The placental membrane is a barrier against some, but not all toxins and infectious agents. • The amniotic sac, a membrane filled with fluid in which the fetus floats, provides a protective buffer for the fetus
How does the developing child’s behavior contribute to its own development?
The Role of Hormones • Hormones play a crucial role in sexual differentiation. • All human fetuses can develop either male or female genitalia, depending on the presence or absence of testosterone.
Fetal Behavior • By 12 weeks after gestation, most of the movements that will be present at birth have appeared. • Prenatal to postnatal continuity • Swallowing amniotic fluid promotes the normal development of the palate and aids in the maturation of the digestive system. • Movement of the chest wall and pulling in and expelling small amounts of amniotic fluid help the respiratory system become functional.
Behavioral Cycles • Become stable during the second half of pregnancy • Circadian rhythms are also apparent • Near the end of pregnancy, sleep and wake states are similar to those after birth
Fetal Sensory Experience • Sensory structures are present relatively early in prenatal development and play a vital role in fetal development and learning. • Visual experience is negligible. • Fetus experiences tactile stimulation as a result of its own activity, and tastes and smells the amniotic fluid. • It responds to sounds from at least the 6th month of gestation.
Evidence of Fetal Learning At 32 weeks gestation, the fetus decreases responses to repeated or continued stimulation, a simple form of learning called habituation.
Evidence of Fetal Learning • Newborn infants have been shown to recognize rhymes and stories presented before birth. • Newborns also prefer smells, tastes, and sound patterns that are familiar because of prenatal exposure.
Newborn States of Arousal • State: The infant’s level of arousal and engagement in the environment • Ranges from deep sleep to intense activity • Is an important influence in the newborn’s exploration of the world
Six States of Arousal • Active sleep • Quiet sleep • Crying • Active awake • Alert awake • Drowsing
Safe Sleep is Essential • Newborns sleep twice as much as young adults • The pattern of two different sleep states changes dramatically: • REM (rapid eye movement) sleep: an active sleep state associated with dreaming in adults and is characterized by quick, jerky eye movements under closed lids • Non-REM sleep: a quiet or deep sleep state characterized by the absence of motor activity or eye movements and by regular, slow brain waves, breathing, and heart rate
REM Sleep • REM sleep constitutes fully 50% of a newborn’s total sleep time and declines rapidly to only 20% by 3 or 4 years of age. • According to autostimulation theory, brain activity during REM sleep in the fetus and newborn makes up for natural deprivation of external stimuli and facilitates the early development of the visual system.
Crying • Early in infancy, crying reflects discomfort or frustration. • Crying gradually becomes more of a communicative act. • With experience, parents become better at interpreting the characteristics of the cry itself.
Crying • Many effective soothing techniques, including swaddling, involve moderately intense and continuous or repetitive stimulation. • Parents of babies with colic should seek social support and relief from frustration—and remember that colic typically ends within a few months.
Infant Mortality • Death during the first year after birth(infant mortality) has become a relatively rare event in the Western industrialized world. • However, rates in the United States are the 20th highest in the world. • African-American infants are more than twice as likely to die before their first birthday as Euro-American babies. • Poverty and lack of health insurance are associated with high rates of infant mortality.
Low Birth Weight • Infants weighing less than 5.5 pounds (2,500 grams) are considered to be of low birth weight (LBW). • LBW infants born at or before 35 weeks after conception are described as premature. • Other LBW infants are referred to as small for gestation age (SGA) when their birth weight is substantially less than the norm for their gestational age.
Low Birth Weight • As a group, LBW babies experience more medical complications, have more developmental difficulties, and present special challenges for parents. • However, the majority of LBW babies turn out quite well. • Extensive parent contact and more touch for infants in neonatal intensive care are widely used interventions.
Parenting LBW Infants • Parenting LBW babies presents special challenges due to parents’ feelings of guilt and inadequacy, the stress of intensive care treatment, and the infants’ disorganized states. • Parents benefit from understanding that their preterm infants’ development will not follow the same timetable as that of a full-term infant, by learning more about infant development, and by seeking social support and intervention programs.
Multiple-Risk Models • Risk factors tend to occur together. • A negative outcome is more likely when there are multiple risk factors. • Despite multiple risk factors, however, some individuals do well.
Poverty as a Developmental Hazard • The existence of multiple risks is strongly related to socioeconomic factors. • In many countries, minority families are overrepresented in the lowest SES levels.
Risk & Resilience • Developmental resilience refers to successful development in the face of multiple and seemingly overwhelming developmental hazards. • Resilient children often experience responsive care from a particular caregiver and possess personal characteristics such as intelligence and responsiveness to others.