An 17th Century View of Conception Prenatal Development Early Views •Preformation—life begins with a new individual already preformed OR •Epigenesis (Aristotle)—new structures and functions emerge during development Conclusion •Embryology—the study of prenatal development Showed the existence of genes and cells Techniques for studying physical and behavioral development in the womb Conception What: Gametes or Germ Cells How: Through the process of conception the egg and a sperm unite Prenatal Development: Period of the Zygote Female reproductive system A simplified illustration of the female reproductive system, with a fetus developing in the uterus (womb). The umbilical cord runs from the fetus to the placenta, which is burrowed deeply into the wall of the uterus. The fetus is floating in amniotic fluid inside the amniotic sac. Periods of Prenatal Development •Zygote Rapid cell division Blastocyst •Embryo gastrulation Cell division Cell migration Cell differentiation Cell death/apoptosis Hormones •Fetus Stages of prenatal development Prenatal Development: Period of the Embryo (Figure adapted with permission from Textbook of Embryology, 5th ed. (p. 87), by H.E. Jordan and J.E. Kindred, 1948, New York: Appleton-Century-Crofts.Copyright © 1948 by Appleton-Century-Crofts.) Prenatal Environment Fetal Experience Touch Taste • Grasping, sucking, rubbing, bumping walls of uterus • Swallows amniotic fluid • Fetus has a sweet tooth Smell • Amniotic fluid has odor of what mom ate • During fetal breathing, amniotic fluid comes into contact with olfactory receptors Sight • Negligible Hearing • Internally generated sounds (mom’s heartbeat, breathing, etc.) • Externally generated sounds (mom’s voice and people talking to her) • Fetus reacts by changes in heartbeat and movement Fetal Learning •Habituation Before Birth After Birth •Around 32 weeks the fetus shows signs of habituation •Hearing: “The Cat in the Hat,” recognizes mom’s voice, languages heard in the womb •Around 37 weeks the fetus shows signs of long-term memory and learning •Smell: Prefers own amniotic fluid •Habituation is measured by •Taste: Recognizes carrot juice changes in heartbeat exposed as a fetus, but not since birth Teratology • Teratogens – Classes of teratogens include – Drugs – Infectious diseases – Mother’s age – Poor nutrition – Other environmental agents Principles of Teratology 1. 2. 3. 4. 5. 6. The effect of a teratogen depends on the genetic makeup of the exposed organism Teratogen effects on development depend on timing (period of 2-8 weeks is particularly sensitive) The effect of a teratogen may be unique The impact of teratogens may be severe Teratogens differ in how they gain access to the fetus Teratogen dosage is related to degree of abnormal development Consequences of Teratogens Street Drugs Therapeutics Caffeine Nicotine Alcohol Environmental Chemicals Babies of drug-addicted mothers are born addicted and are likely to have developmental problems Drugs such as thalidomide may induce abnormalities Some risk is associated with caffeine Can affect growth, increase risk of premature delivery Can lead to Fetal Alcohol Syndrome Mercury, lead, and PCBs are harmful to the fetus Natural Teratogens • Maternal infectious diseases – Rubella can damage the CNS of the fetus, sensitive period is 2-8 weeks – Herpes virus can cause brain abnormalities and blindness – HIV can produce facial abnormalities • Nutrition – Poor prenatal nutrition results in unfavorable development, low brain weight, and higher rates of spontaneous abortion Parental Age Effects (Figure reprinted with permission from: “Paternal Age Effect” by J.M. Friedman, Obstetrics and Gynecology, vol 57, 1981, p 746.) Fetal Alcohol Syndrome • Alcohol is the most widely used drug known to harm the fetus – Third major cause of birth defects – Leading cause of congenital mental retardation • Consumption of alcohol during pregnancy can result in Fetal Alcohol Syndrome (FAS) • Constellation of limb and facial deformations, failure to thrive, mental retardation, and learning disabilities • Chronic use of alcohol increases the risk of FAS to 50%; Risks associated with low levels of alcohol are unknown Screening Methods • • • • Ultrasound Imaging Amniocentesis Chorionic Villus Sampling Test-tube Screening Birth •Is being born as painful as giving birth? The baby experiences squeezing Reduces size of head to pass through mother’s pelvic bones Stimulates the production of hormones which help withstand hypoxia and regulate breathing Inhibits the fetus from breathing until out of birth canal Squeezing of infant’s body forces amniotic fluid from lungs to prepare for first breath •Diversity of Childbirth Practices Stages of Birth “At Risk” Issues • Babies may have two different risks: – Risk for major physical malformations – At risk for developmental delays, and for cognitive and social problems • Indicators of at risk status Newborn Assessments • Apgar exam • Prechtl test • Brazelton Neonatal Behavioral Assessment Scale The Newborn •States •Sleep REM Sleep 50% of a newborn’s total daily sleep •Sudden Infant Death Syndrome (SIDS) Newborn states The average proportion of time, in a 24-hour day, that Western newborns spend in each of six states. There are substantial individual and cultural differences in how much time babies spend in the different states. Total sleep and proportion of REM and non-REM sleep across the life span •Crying How Much? What Does It Mean? What Should You Do? Newborn Reflexes • Some reflexes are evident at birth but disappear by age one; These reflexes can index the development of the infant – Rooting reflex – Palmar reflex – Moro reflex Motor Development • Postural development and locomotion • Prehension – Proximodistal direction – Cephalocaudal direction Physical Growth (Figure adapted with permission from “Standards for Growth and Growth Velocity” by J.M. Tanner, R.H. Whitehouse, and M Takaishi, 1966, Archives of Disease in Childhood, 41, p 467. Copyright © 1966 by Archives of Disease in Childhood) Development of Locomotion (Figure adapted with permission from “Early Development of Locomotion: Significance of Prematurity, Cerebral Palsy, and Sex” by R.H. Largo, L. Molinari, M. Weber, L.C. Pinto, and G. Duc, 1985, Developmental Medicine and Child Neurology, 27, pp 183-191, figure 2. Copyright © 1985 by MacKeith Press.) Brain Development • Three phases of brain development: – Cell production – Cell migration – Cell elaboration Cortical Function Negative Outcomes at Birth •Infant Mortality Poverty Healthcare •Low Birth Weight (LBW)—less than 5½ pounds at birth Types Premature—less than or equal to 35 weeks gestation Small for gestational age (SGA)—weight less for gestational age whether preterm or full-term •Long-term Outcomes As a group LBW babies have more developmental problems (cognitive, social, and/or behavioral) Majority of LBW babies turn out fine •Risk Multiple Risk Model Poverty Resilience Developmental Resilience Responsive care from someone Personal characteristics (intelligence, responsiveness to others, believe can achieve goals) Multiple risk factors Children who grow up in families with multiple risk factors are more likely to develop psychiatric disorders than children from families with only one or two problematic characteristics (Rutter, 1979).