Week 1 - Prenatal Development[1]

Prenatal Development: Conception to Birth

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Thinking About Development Learning Objectives – What are the fundamental issues of development that scholars have addressed throughout history? – What are the basic forces in the biopsychosocial framework? How does the timing of these forces make a difference in their impact?

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Thinking About Development Three Recurring Issues in Human Development Nature vs. Nurture – What is the role of heredity and how does it compare with the role of environment on human development?

Continuity vs. Discontinuity – Does development consist of a smooth progression (continuity), or is it a series of abrupt shifts (discontinuity)? Table of Contents

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Thinking About Development Three Issues (cont.) Universal vs. Context-Specific Development – Are differences in development across cultures simply variations on a universal developmental process? OR: – Does development take different paths dependent upon environmental context?

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Nature and Nurture: The Enduring Developmental Issue Environment – the influence of experience to which a child is exposed

Heredity – those influences based on genetic makeup of an individual that affect growth and development throughout life

Nature-Nurture Issue – the issue of the degree to which environment and heredity influence behavior Table of Contents

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Thinking About Development Basic Forces in Human Development: The Biopsychosocial Framework Biological Forces: – Genetic and health-related factors

Psychological Forces: – Perceptual, cognitive, emotional, and personality factors

Sociocultural Forces: – Interpersonal, societal, cultural, and ethnic factors

Life-Cycle Forces: – Same events many people experience, affecting people of different ages differently Table of Contents

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Thinking about Development The Biopsychosocial Framework None of these forces alone adequately explain the process of development. Human development is the combined effects of Biological, Psychological, Sociocultural, and Life-Cycle forces. Each of these factors impact the others.

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Biological Foundations: Heredity, Prenatal Development, & Birth

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In the Beginning Learning Objectives – What are chromosomes and genes? How do they carry hereditary information from one generation to the next? – What are common problems involving chromosomes and what are their consequences? – How is children’s heredity influenced by the environment in which they grow up?

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In the Beginning Mechanisms of Heredity Human eggs contain 23 chromosomes selected from the mother’s 46. One chromosome is selected from each of the 23 pairs of chromosomes. Human sperm contain 23 chromosomes selected from the father’s 46. One chromosome is selected from each of the 23 pairs. Table of Contents

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In the Beginning Conception The human egg and sperm unite, resulting in a zygote which contains a complete set of 46 chromosomes. The first 22 pairs of chromosomes are called autosomes. The 23 pair determines the gender of the child and are called the sex chromosomes. The 46 chromosomes contain around 30,000 genes.

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In the Beginning The 23rd Pair of Chromosomes Males carry XY chromosomes. X from mother and Y from father. Females carry XX chromosomes. X from mother and X from father.

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In the Beginning Inheritance The complete set of inherited traits are called the child’s genotype. How the traits are expressed is called the child’s phenotype and is the combined effects of genotype and environmental influences.

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In the Beginning Alleles The child’s characteristics are determined by the interaction of genes on the two chromosomes in a pair. Each chromosome of a pair contains one parent’s contribution to a specific trait. When the genes are the same they are called homozygous. When different, they are called heterozygous. Table of Contents

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In the Beginning Homozygous Alleles When alleles are the same, both of the child’s parents have contributed similar genes for a trait.

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In the Beginning Heterozygous Alleles The parents have contributed different versions of the trait. The phenotype of the child is determined by which version of the trait is more dominant. When one allele is not clearly dominant over the other, incomplete dominance results.

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In the Beginning Behavioral Genetics The study of the inheritance of behavioral and psychological traits.

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In the Beginning Polygenetic Inheritance When many genes affect the phenotype of a trait. Many psychological and behavioral characteristics are polygenetic and are impossible to trace to a single gene.

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In the Beginning Twins Dizygotic (fraternal) twins come from two different eggs fertilized by two different sperm. Monozygotic (identical) twins come from the union of one egg and one sperm that splits in two, soon after conception.

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In the Beginning What Twins Can Teach Us Fraternal twins, while they share much of the same experience and environment, have no more genetic similarity than other siblings. Identical twins share much of the same experience but are also genetically identical.

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In the Beginning Twins and Adoption Studies Twin studies emphasize the importance of heredity in development. Studying the similarity of adopted children to their adoptive parents helps to demonstrate the role of experience.

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In the Beginning Genetic Disorders Inherited Disorders involve dominant or recessive alleles for conditions such as Sickle-Cell Disease, PKU, and Huntington’s Disease. Extra, missing, or damaged chromosomes result in abnormalities of development (e.g. Down Syndrome, Turner’s Syndrome, & Klinefelter’s Syndrome). Table of Contents

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In the Beginning Heredity is Not Destiny Genes probably do not directly cause behavior. Instead they set conditions such as physiology that affect abilities and choices. Reaction Range refers to the fact that phenotype is affected by environment factors to produce phenotype.

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In the Beginning Three Types of Relationships Between Genetics and Environment In Passive Gene-Environment Relation, parents contribute both genetics and environmental conditions to their children. In Evocative Gene-Environment Relation, genotypes tend to evoke reactions or responses from the environment. An Active Gene-Environment Relation results in individuals who actively seek environments related to their genetic makeup (Niche-Picking). Table of Contents

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From Conception to Birth Learning Objectives What happens to a fertilized egg in the first two weeks after conception? When do body structures and internal organs emerge in prenatal development? When do body systems begin to function well enough to support life?

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From Conception to Birth Periods of Prenatal Development Period of the Zygote (Weeks 1-2) – After fertilization, the zygote travels down the fallopian tube and is implanted in the uterine wall.

Period of the Embryo (Weeks 3-8) – Body structures, internal organs, and the three layers of the embryo (ectoderm, mesoderm, & endoderm) develop. – The amniotic sac fills with fluid and the umbilical cord connects the embryo to the placenta. Table of Contents

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From Conception to Birth Periods of Prenatal Development (cont.) Period of the Fetus (Week 9-Birth) – – – –

Week 9- Differentiation of the ovaries and testes. Week 12- Circulatory system begins to function. Week 16- Movement felt by mother. Week 32- Age of viability.

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Three Stages of Development : – Ovulation to implantation: the ovum travels down the fallopian tube, is fertilized by a sperm, and is then implanted within the wall of the uterus – Embryonic period: implantation to 8 weeks – Fetal stage: 8 weeks to birth

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One month An embryo consisting of two layers of cells from which all the organs and body parts will develop. • Embryo is 1/4 inch in length • Heart, digestive system, backbone and spinal cord begin to form • Placenta (sometimes called "afterbirth") begins to develop • The single fertilized egg is now 10,000 times larger than size at conception Table of Contents

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Two MonthS Embryo is now about the size of a kidney bean and is constantly moving. •Enbryo is 1-1/8 inches long •Heart is functioning •Eyes, nose, lips, tongue, ears and teeth are forming •Penis begins to appear in boys •Embryo is moving, although the mother can not yet feel movement

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Three monthS Fetus’ tiny, unique fingerprints are now in place. • Fetus is 2 1/2 to 3 inches long • Weight is about 1/2 to 1 ounce • Nails start to develop and earlobes are formed • Arms, hands, fingers, legs, feet and toes are fully formed • Eyes are almost fully developed •Fetus has developed most of his/her organs and tissues •Fetus’ heart rate can be heard at 10 weeks with a special instrument called a Doppler Table of Contents

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FOUR MONTHS

Fetus’ skeleton is starting to harden from rubbery cartilage to bone. •Fetus is 6 1/2 to 7 inches long •Weight is about 6 to 7 ounces •Fetus is developing reflexes, such as sucking and swallowing and may begin sucking his/her thumb •Fingers and toes are well defined •Sex is identifiable •Skin is bright pink, transparent and covered with soft, downy hair •Although recognizably human in appearance, the baby would not be able to survive outside the mother's body

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FIVE MONTHS Eyebrows and eyelids are now in place. Baby would now be more than 10 inches long if you stretched out her legs. •Fetus is 8 to 10 inches long •Weight is about 1 pound •Hair begins to grow on baby's head •Mother begins to feel fetal movement •Internal organs are maturing •Eyebrows, eyelids and eyelashes appear

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SIX MONTHS Fetus’ wrinkled skin is starting to smooth out as he puts on baby fat. •Fetus is 11 to 14 inches long •Weight is about 1 3/4 to 2 pounds •Eyelids begin to part and eyes open sometimes for short periods of time •Skin is covered with protective coating called vernix •Baby is able to hiccup

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SEVEN MONTHS Fetus can open and close eyes and follow a light. •Fetus is 14 to 16 inches long •Weight is about 2 1/2 to 3 1/2 pounds •Taste buds have developed •Fat layers are forming •Organs are maturing •Skin is still wrinkled and red •If born at this time, baby will be considered a premature baby and require special care

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EIGHT MONTHS Fetus’ layers of fat are filling him out, making him rounder, and his lungs are well developed. •Fetus is 16 1/2 to 18 inches long •Weight is about 4 to 6 pounds •Overall growth is rapid this month •Tremendous brain growth occurs at this time •Most body organs are now developed with the exception of the lungs •Movements or "kicks" are strong enough to be visible from the outside •Kidneys are mature •Skin is less wrinkled Table of Contents Exit

NINE MONTHS Babies vary widely in size at this stage •Baby is 19 to 20 inches long •Weight is about 7 to 7 1/2 pounds •The lungs are mature •Baby is now fully developed and can survive outside the mother's body •Skin is pink and smooth •Baby settles down lower in the abdomen in preparation for birth and may seem less active Table of Contents

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Time

Development

1st -2nd weeks

one week old zygote are called blastocyst. During the second week, the blastocyst becomes firmly implanted in the wall of the uterus. From its outer layer of cells, the placenta, an umbilical cord, and the amniotic sac begin to develop. The inner cell layer develops into the embryo itself.

3rd week

neural induction: a chemical signal is sent from the mesoderm to the ectoderm thus signalling the onset of nervous system development. Developing brain’s electrical activity helps to shape the structure of the brain.

4th week

the heart begins to beat- the embryo’s first movement

5th week

eyes and ears begin to emerge, body buds give clear evidence of becoming arms and legs, and the head area is the largest part of the rapidly growing embryo.

6th -7th weeks

fingers begin to appear on the hands, the outline of toes is seen, and the beginnings of the spinal cord are visible. In the germinal period, the number and differentiation of cells rapidly increase; in the embryonic period, the organs are formed, a process called organogenesis

8th week

95 percent of the body parts are formed and general body movement are detected. During these weeks embryonic tissues is particularly sensitive to any foreign agents during differentiation, especially beginning at the third or fourth week of the Table of Contents Exit pregnancy.

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Development

3rd month

the fetus grows rapidly both in height and weight. The sex organs appear during the third month, and it is possible to determine the baby’s sex. Visible sexual differentiation begins, and the nervous system continues to increase in size and complexity.

4th - 5th months

The fetus now swallows, digests, discharges urine. The fetus is now active- sucking, turning its head, and pushing with hands and feetand the mother is acutely aware of the life within her. The fetus produces specialized cells: red blood cells to transport oxygen and white blood cells to combat disease

6th – 7th months

Rapid growth continues in the sixth month with the fetus gaining another 2 inches and 1 pound, but slows during the seventh month. Viability, the ability to survive if born, is attained. After six months very few new nerve and muscle cells appear, since at birth the nervous system must be fully functioning to ensure automatic breathing.

8th – 9th months

organ development prepares the fetus for the shock of leaving the sheltered uterine world. The senses are ready to function; some, in fact, are already functioning. Table of Contents Exit

Influences on Prenatal Development Learning Objectives How is prenatal development influenced by a pregnant woman’s age, her nutrition, and the stress she experiences while pregnant? How do diseases, drugs, and environmental hazards sometimes affect prenatal development? What are some general principles affecting the ways prenatal development can be harmed? How can prenatal development be monitored? Can abnormal prenatal development be corrected? Table of Contents

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Genetic Influences on the Fetus Phenylketonuria (PKU) • cannot produce a required enzyme

Sickle-cell anemia • abnormal shape of red blood cells

Tay-Sachs disease • body’s inability to break down fat

Down’s Syndrome • extra chromosome

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Prenatal Environmental Influences Mother’s nutrition and emotional state Illness of mother Mother’s use of drugs Birth complications

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Genetic Disorders Down syndrome  is a genetic disorder that is not aborted Individuals usually have an extra 21st chromosome.  Down syndrome individuals have a distinctive appearance  and are mentally retarded. Disorders of the sex chromosomes  are more common  because these chromosomes contain much less genetic  material.  

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Single gene­pair inheritance dominant genes­­ if even one is inherited will produce the  effect (Gregor Mendel)  recessive genes­­ need one from both parents to produce  effect sickle­cell disease­­ recessive disorder alters shape of  blood cell carriers—do not have trait but can transmit to children  via recessive gene

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Heredity is Not Destiny:  Genes and  Environment PKU, an inherited disorder­­ phenylalanine  accumulates in the body, damaging the nervous  system.   Mental retardation can be avoided with a diet  that is low in phenylalanine.   PKU demonstrates the concept of reaction  range  –  the outcome of heredity depends upon the  environment in which development occurs.

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“incomplete dominance” ­­ neither gene in pair is completely dominant or recessive  (e.g., sickle­cell trait);  one is mostly dominant but not completely  (e.g. in times when lack oxygen/ vigorous exercise, then  less dominate gene may be expressed ) 

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Teratogens Teratogens are environmental substances that can cause birth defects in the developing fetus – Maternal alcohol use leads to fetal alcohol syndrome (facial defects, low IQ, neurobehavioral defects) – Nicotine exposure leads to premature births, low birth weights, fetal deaths, cognitive problems, behavioral abnormalities

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Influences on Prenatal Development Teratogens Drugs – Alcohol, aspirin, caffeine, narcotics, marijuana, & nicotine. – May cause Fetal Alcohol Syndrome, cognitive deficits, low birth weight, slowed growth, and other effects.

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Influences on Prenatal Development Teratogens: Diseases AIDS, Cytomegalovirus, Genital Herpes, Rubella (German Measles), Syphilis. Effects include neurological disorders, deafness, blindness, mental disability, damage to bones, eyes, ears, or heart.

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Influences on Prenatal Development Teratogens: Environmental Hazards Lead, Mercury, PCBs, X-Rays. Effects may include mental disability, retarded growth, cerebral palsy, impaired memory and verbal skill, retarded growth, and leukemia.

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Influences on Prenatal Development How Teratogens Influence Prenatal Development The effect of the teratogen depends upon the genotype of the organism (e.g., Thalidomide). The impact of teratogens changes over the course of prenatal development. Each teratogen affects a specific aspect of prenatal development. The impact of teratogens depends on the dosage. Damage from teratogens is not always evident at birth. Table of Contents

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Influences on Prenatal Development General Risk Factors Nutrition – Inadequate maternal nutrition may result in premature birth and low birth weight. – Lack of folic acid may increase risk of spina bifida.

Stress – Studies show extreme maternal stress is associated with low birth weight and premature births. Table of Contents

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Influences on Prenatal Development General Risk Factors (cont.) Mother’s Age – Older mothers are more likely to have difficulty getting pregnant, miscarriages, and stillbirths. – Nearly 50% of pregnancies among women in their 40’s and 50’s result in miscarriage.

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Influences on Prenatal Development Prenatal Diagnosis and Treatment Genetic Counseling – Helps to assess the chances of inherited disorders.

Prenatal Diagnosis – Ultrasound is the use of soundwaves to produce a picture of the fetus. – Amniocentesis allows the taking of a sample of the amniotic fluid. – Chorionic Villus Sampling is taken from the placenta and can be done earlier than amniocentesis.

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Influences on Prenatal Development Prenatal Diagnosis and Treatment (cont.) Fetal Medicine – Administering medicine to the fetus. – Fetal Surgery to correct spina bifida and circulatory problems. – Genetic Engineering involves replacing defective genes with synthetic normal genes.

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Labor and Delivery Learning Objectives What are the different phases of labor and delivery? What are “natural” ways of coping with the pain of childbirth? Is childbirth at home safe? What are some complications that can occur during birth?

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Labor and Delivery Stages of Labor Stage 1 lasts 12-24 hours for the first birth and includes contractions and the enlargement of the cervix to approximately 10 centimeters. Stage 2 includes the actual birth of the baby and lasts about an hour. Stage 3 lasts a few minutes and involves expelling of the placenta. Table of Contents

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Labor and Delivery Approaches to Childbirth Childbirth Classes – Explains what happens during pregnancy and delivery. – Teaches techniques to manage the pain of childbirth. The emphasis is on natural methods, relaxation, and coaching. – Studies show that mothers who attend childbirth classes typically use less medication. Table of Contents

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Labor and Delivery Approaches to Childbirth Birthing Alternatives – Home Births • Less Expensive • Parents have more control over the conditions • Birth problems are no more common at home than at the hospital when pregnancy has been problem-free.

– Birthing Centers • More home-like than hospitals, but in a clinic setting independent of hospitals. Table of Contents

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Labor and Delivery: Birth Complications Hypoxia, or inadequate blood and oxygen to baby. Complications may result in cesarean section (C-section) Births before the 36th week are called premature or preterm.

Babies weighing less than 5.5 pounds have low birth weight. Babies weighing less than 3.3 pounds have very low birth weight. Below 2.2 pounds is called extremely low birth weight.

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Labor and Delivery Infant Mortality Infant Mortality is the number of infants out of 1,000 births that die before the age of 1 year. U.S. mortality rate is about 1%, or 9 of 1000. 15 industrialized nations have lower infant mortality than U.S. Possible factors include low birth weight resulting from a lack of free or inexpensive prenatal care and fewer paid leaves of absence for pregnant women.

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