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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 DevelopmentNature 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)?

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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

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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

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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.

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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

AllelesThe 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.

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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).

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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 EnvironmentIn 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).

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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 DevelopmentPeriod 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.

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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 monthOne monthAn embryo consisting oftwo layers of cells fromwhich all the organs and bodyparts 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

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Two MonthSTwo 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 monthSThree monthSFetus’ 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

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FOUR MONTHSFOUR MONTHSFetus’ 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 MONTHSFIVE 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 MONTHSSIX 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 MONTHSSEVEN MONTHSFetus 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 MONTHSEIGHT MONTHSFetus’ 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

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NINE MONTHSNINE MONTHSBabies 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

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TimeTime DevelopmentDevelopment11stst -2 -2ndnd weeks weeks one week old zygote are called blastocyst. During the second week, the blastocyst 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 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 placenta, an umbilical cord, and the amniotic sac begin to develop. The inner cell layer develops into the embryo itself.develops into the embryo itself.

33rdrd week week neural induction: a chemical signal is sent from the mesoderm to the ectoderm thus 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 signalling the onset of nervous system development. Developing brain’s electrical activity helps to shape the structure of the brain. activity helps to shape the structure of the brain.

44thth week week the heart begins to beat- the embryo’s first movement the heart begins to beat- the embryo’s first movement

55thth week week eyes and ears begin to emerge, body buds give clear evidence of becoming arms and 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.legs, and the head area is the largest part of the rapidly growing embryo.

66thth -7 -7thth weeks weeks fingers begin to appear on the hands, the outline of toes is seen, and the beginnings of 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 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 cells rapidly increase; in the embryonic period, the organs are formed, a process called organogenesis organogenesis

88thth week week 95 percent of the body parts are formed and general body movement are detected. 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 these weeks embryonic tissues is particularly sensitive to any foreign agents during differentiation, especially beginning at the third or fourth week of the during differentiation, especially beginning at the third or fourth week of the pregnancy. pregnancy.

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TimeTime DevelopmentDevelopment

33rdrd month month the fetus grows rapidly both in height and weight. The sex organs the fetus grows rapidly both in height and weight. The sex organs appear during the third month, and it is possible to determine the appear during the third month, and it is possible to determine the baby’s sex. Visible sexual differentiation begins, and the nervous baby’s sex. Visible sexual differentiation begins, and the nervous system continues to increase in size and complexity.system continues to increase in size and complexity.

44thth - 5 - 5thth months months The fetus now swallows, digests, discharges urine. The fetus is now The fetus now swallows, digests, discharges urine. The fetus is now active- sucking, turning its head, and pushing with hands and feet- active- sucking, turning its head, and pushing with hands and feet- and the mother is acutely aware of the life within her. The fetus and the mother is acutely aware of the life within her. The fetus produces specialized cells: red blood cells to transport oxygen and produces specialized cells: red blood cells to transport oxygen and white blood cells to combat disease white blood cells to combat disease

66thth – 7 – 7thth months months Rapid growth continues in the sixth month with the fetus gaining Rapid growth continues in the sixth month with the fetus gaining another 2 inches and 1 pound, but slows during the seventh month. another 2 inches and 1 pound, but slows during the seventh month. Viability, the ability to survive if born, is attained. After six months Viability, the ability to survive if born, is attained. After six months very few new nerve and muscle cells appear, since at birth the very few new nerve and muscle cells appear, since at birth the nervous system must be fully functioning to ensure automatic nervous system must be fully functioning to ensure automatic breathing.breathing.

88thth – 9 – 9thth months months organ development prepares the fetus for the shock of leaving the organ development prepares the fetus for the shock of leaving the sheltered uterine world. The senses are ready to function; some, in sheltered uterine world. The senses are ready to function; some, in fact, are already functioning. fact, are already functioning.

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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?

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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 abortedIndividuals 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 gene-pair inheritance

dominant genes-- if even one is inherited will produce the effect (Gregor Mendel) recessive genes-- need one from both parents to produce effectsickle-cell disease-- recessive disorder alters shape of blood cellcarriers—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., sickle-cell 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.

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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.

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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 LaborStage 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.

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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.

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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.

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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.