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Chapter 4

CH4 Prenatal Development.doc

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Department
Psychology
Course
PSYC 2450
Professor
Anneke Olthof
Semester
Winter

Description
CH4 Prenatal Development, Birth, and Newborns' Readiness for Life - prenatal development-development that occurs between moment of conception and birth - Inside womb, three stages as well, but stages pass quickly as organism becomes a zygote, then embryo, and finally fetus. - transition from embrytofetus occurs a8 weeks, - full month before pregnant woman enters second trimester of pregnancy often, before aware she is pregnant. -foundations for all of embryo's major organs formed -rest of the prenatal period time of growth, developing function, and refinement of organs and structures From Conception to Birth -moment of conception, take approximately 266 days for zygote to become a fetus readtobe born. -period of zygote (or germinal period), lasts from conception through implantation, when zygote becomes firmly attached to wall of uterus - 10 to 14 days -period of the embryo, beginning of third week through end of eighth -all major organs formed , heart begins to beat -period of fetus, lasts from ninth week of pregnancy until child is born The Period of the Zygote -two cells and all resulting cells continue to divide, forming ball-shaped structure, blastocyst60cto80icells w/in4 days of conception -inner layer of blastocyst, embryonic disk, becomes embryo, whereas outer layer of cells develop into tissues that protect and nourish embryo Implantation -blastocyst approaches uteru6 to10 days after conception, small, burrlike tendrils emerge from outer surface tapping mother's blood supply -This is implantation -" window of implantation" during which blastocyst must communicate (biologically) with uterine wall, -takes about 48 hours , occu7sto10 days after ovulation, entire process completing ab10to 14 days after ovulation -nearly three zygotes out of four, including most of abnormal ones, fail to survive initial phase of prenatal development Development of Support Systems -blastocyst's outer layer rapidly forms four major support structures that protect and nourish -One membrane, amnion, watertight sac fills w/ fluid from mother's tissues -purposes of sac and its amniotic fluid : cushion against blows, regulate temperature, provide weightless environment for embryo to move -in watery environment is balloon-shaped yolk sac - produces blood cells until embryo capable of producing its own. -attachedtothird membrane, the chorion, surrounds amnion , eventually becomes lining of placenta -allantois, forms embryo's umbilical cord. Purpose of the Placenta -fed by blood vessels from mother and embryo, although hairlike villi act as barrier prevents these two bloodstreams from mixing. -barrier is semipermeable, -umbilical cord transports carbon dioxide and metabolic wastes from embryo. -waste products cross placental barrier, enter mother's bloodstream, eventually expelled The Period of the Embryo -lasts from implantation (roughly third week) through eighth week of pregnancy. -third week, embryonic disk rapidly differentiating into three cell layers. -ectoderm, will become nervous system, skin, and hair. -mesoderm, will become muscles, bones, and circulatory system -endoderm, will become digestive system, lungs, urinary tract, and other vital organs -portion of the ectoderm folds into neural tube - becomes the brain and spinal cord -end of fourth week, heart has formed and begun to beat. -embryo about .6cm but already 10 000times size of zygote The Second Month -becomes much more human in appearance -grows about 1mm per day -primitive tail appears, soon enclosed by protective tissue , becomes tip of backbone, the coccyx -middle of fifth week, eyes have corneas and lenses -seventh week, ears well formed, embryo has rudimentary skeleton. -Limbs developing from body outward; upper arms appear first, followed by forearms, hands, -seventh and eighth embryo's sexual development begins w/ appearance of genital ridge indifferent gonad. -end of second month, embryo slightly more than 2.5 cm long and weighs less than 7.0g. Period of the Fetus -seven months of pregnancy, or period of fetus -all major organ systems begin to function and fetus begins to move, sense , behave -individuality emerges as different fetuses develop unique characteristics, ex different patterns of movement and different facial expressions. The Third Month -organ systems formed earlier continue growth , become interconnected -coordination b/w nervous and muscular systems allow fetus to perform many interesting manoeuvre -male testes secrete testosterone-male sex hormone responsible for development of a penis and scrotum -end of third month, sex of a fetus detected by ultrasound The Second Trimester: The Fourth through Sixth Months -13th through 24th weeks of pregnancy; second trimester. -16 weeks, fetus approximately 20 to 25 em long , weighs about 170 g. -15 or 16 weeks through 24 or 25, simple movements of tongue, lips, pharynx, and larynx increase in complexity and coordination -Infants born prematurely may have difficulty breathing suckling ; exit womb early stage in development of these skill ; haven't had enough time to practice -fetus begins kicking may be strong enough tobe felt by pregnant woman. -end of 16th week, fetus assumed distinctly human appearance, although stands virtually no chance of surviving outside womb -fifth and sixth months, nails harden, skin thickens, and eyebrows, eyelashes, and scalp hair appear. -20 weeks, sweat glands functioning, heartbeat often strong enough to be heard -fetus now covered w/ white cheesy substance called vernix and fine layer of body hair lanugo -Vernix protects skin against chapping exposure to amniotic fluid -lanugo helps vernix stick to skin. -end of sixth month, fetus's visual and auditory senses clearly functional. - some ability to discriminate b/w sounds. - ability may indicate presence of a rudimentary, short-term memory system The Third Trimester: The Seventh through Ninth Months -all organ systems mature rapidly, preparing fetus for birth -22 and 28 weeks after conception (usually seventh month), fetuses reach age of viability- point which survival outside uterus is possible -28- to32-week-old begin to show better organized and predictable cycles of heart rate activity; gross motor activity; and sleepiness/waking activity -indicate developing nervous systems sufficiently well organized to allow survival should birth be premature -many fetuses born require oxygen assistance -pulmonary alveoli (air sacs) in lungs too immature to inflate and exchange oxygen for carbon dioxide on their own -end of seventh month, weighs just over 1.8 kg and about 40.0 to 43.0 em long. - month later grown to 46.0 em and put on another 0.5 to 1.0 kg. -comes from a padding of fat deposited beneath skin later helps to insulate newborn infant from changes in temperature. - most comfortable position likely head-down posture at base of uterus, w/ limbs curled up -stages of development through developing organism passes do not correspond to trimester stages used to describe pregnant woman's experience -developing organism passes through all three stages of prenatal development in pregnant woman's first trimester. Environmental Influences on Prenatal Development Teratogens -teratogens external agents ex viruses, drugs, chemicals, radiation can harm developing embryo or fetus -causing physical deformities, severely retarded growth, blindness, brain damage, and even death -sensitive period during which organism quite susceptible to certain environmental influences; outside period, same environmental influences must stronger to produce comparable effects. - Olli Heinonen : concluded many birth defects found among children in sample were anytime malformations-problems could have been caused by teratogens at any point during prenatal period Maternal Diseases -Some disease agents capable of crossing placental barrier , doing much more damage to a developing embryo or fetus than pregnant woman herself -embryo or fetus has immature immune system cannot produce enough antibodies to combat infections effectively Rubella -rubella (German measles) disease has little effect on mother but may cause number of serious birth defects in unborn children who exposed in first 3 to 4 months of pregnancy. 1941 McAllister Gregg, noticed many mothers who had rubella (German measles) early in pregnancy delivered babies who were blind -doctors began to notice pregnant rubella patients regularly bore children w/ variety of defects : blindness, deafness , cardiac abnormalities, and mental retardation. -most dangerous during first trimester. -60 to85 %of babies infected first 8 weeks of pregnancy will have birth defects, compared to 50 %infected in third month ;16 percent weeks 13 to 20 clearly illustrates sensitive-period principle. - eye and heart defects greatest in first 8 weeks; deafness in 6 throug13. Other Infectious Diseases -toxoplasmosis : by a parasite found in many animals. -may acquire parasite eating undercooked meat or handling feces of family cat that has eaten infected animal -produces only mild cold like symptoms in adults, can cause severe eye and brain damage if transmitted to during first trimester, -induce miscarriage if strikes later in pregnancy Sexually Transmitted Diseases/Infections -capable of producing serious birth defects or otherwise compromising developmental outcomes -syphilis, genital herpes, acquired Immune deficiency syndrome (AIDS)- especially hazardous. - syphilis : pregnant women who receive no treatment run risk of miscarrying or giving birth to child who has serious eye, ear, bone, heart, or brain damage - genital herpes : kills about 1/3 of all infected newborns , causes disabilities: blindness, brain damage, and other serious neurological disorders in another 25 to 30 % acquired immunedeficiency syndrome (AIDS): - ways of catching - 1) prenatally, through placenta; (2) while giving birth, when potential exchange of blood child as umbilical cord separates from placenta; -(3) after birth, passed through mother's milk during breast-feeding - fewer than 25 percent of babies born to HIV-infected mothers infected themselves. - more than half of all HIV-infected infants living beyond age 6, w/ fair percentage surviving into adolescence. - virtually all HIV-infected youngsters eventually die from complications of infection, Drugs The Thalidomide Tragedy. 1960 mild tranquillizer, sold over counter, said to alleviate nausea and vomiting in morning - Thousands who had used thalidomide during first two months of pregnancy gave birth to babies w/ severe birth defects. - often badly deformed eyes, ears, noses, and hearts, many displayed phocomelia- structural abnormality in which all or parts of limbs missing and feet or hands may be attached directly to torso, similar to flippers. - waited until 40th day before using thalidomide, usually not affected Other Common Drugs - 60 % of pregnant women take at least one prescription or OTC drug. - Heavy use of aspirin linked to fetal growth retardation, poor motor control, and even infant death - use of ibuprofen in third trimester increases risk of a prolonged delivery and pulmonary hypertension in newborns - heavy use of caffeine (, more than four soft drinks/ cups of coffee per day) to miscarriage and low birth weight - antidepressants containing lithium can produce heart defects taken in first trimester - oral contraceptives contain female sex hormones, -if woman takes the pill w/ knowing she is pregnant, her unborn child faces slightly increase risk of heart defects and other minor malformations - serious long-term effects diethylstilbestrol (DES)- active ingredient of drug widely prescribed for prevention of miscarriages b/w mid-1940s and 1965. - 1971clearly established 17- to 21-year-old females whose mothers used DES at risk for developing abnormalities of reproductive organs ex rare form of cervical cancer - fewer than 1 in 1,000 DES daughters developed disease thus far - DES daughters who become pregnant more likely to miscarry or deliver prematurely. - no conclusive evidence prenatal exposure to DES causes cancer in sons, -small number of men exposed to DES before birth developed minor genital trait abnormalities Alcohol. - affects development of fetus directly and indirectly by compromising function of placenta - Fetal Alcohol Syndrome (FAS) : group of serious congenital problems commonly observed in offspring of mothers who abuse alcohol during pregnancy. - fetal alcohol effects (FAE) group of mild congenital problems sometimes observed in children of mothers who drink sparingly to moderately during pregnancy. - referred to as Alcohol Related Neurodevelopmental Disorder (ARND) - neurobehavioural defects in absence of characteristic physical signs - most noticeable characteristics of FAS defects : microcephaly (small head) , malformations of heart, limbs, joints, and face -likelytodisplay excessive irritability, hyperactivity, seizures, and tremors. -smaller and lighter than normal, physical growth lags to normal age-mates. -score well below average in intelligence throughout childhood and adolescence, more than 90 % display major adjustment problems -How much can pregnant woman drink w/o harming baby? -no safe amount of alcohol can be consumed during pregnancy -drinking can affect male reproductive system, leading to reduced sperm motility, lower sperm count, abnormally formed sperm. -newborns whose fathers use alcohol likely to have lower birth weights than newborns whose fathers do not Cigarette Smoking. -1996-1997, 21.3 percent of children under age of 3 had mothers reported smoking during pregnancy -90.9 percent reported smoking in third trimester of pregnancy, when negative effect on fetal health is greatest -positive association b/w smoking during first trimester and cleft lip, with or without cleft palate -abnormal lung function and hypertension in newborns of women who smoked during pregnancy -smoking retards rate of fetal growth , increases risk of miscarriage or death shortly after birth in otherwise normal infants , - leading contributor to growth retardation and low-birth-weight deliveries -associated w/ higher incidences of ectopic pregnancies & sudden infant death syndrome - affect regulation of autonomic activity in neonates. -hearts of neonates exposed to nicotine in utero beat more rapidly than those not exposed to nicotine -Fetal concentrations of nicotine may be much as 15 percent higher than those of smoking women -Newborn infants of fathers who smoke likely to smaller than normal - women become recipient of 2nd hand smoke Illicit Drugs. -12.5 % of infants born in downtown Toronto, 3 % born in suburban nurseries prenatal exposure to drugs such as cocaine -brain tissue of human fetuses reveals marijuana use during pregnancy associated w/ changes in functioning of basal nucleus of amygdala, - an area of brain involved in regulation of emotional behaviour -changes prevalent in male fetuses, may indicate utero exposure to marijuana causes impairment of emotional regulation, especially for boys -compared to children not exposed in utero, 10-year-olds whose mothers smoked one or more joints per day during first trimester exhibited poorer performance on achievement tests for reading and spelling. -evaluations of classroom performance lower than those nonexposed peers. - Second-trimester marijuana use assoc deficits in reading comprehension + underachievement. -heroin, methadone, etc : do not appear to produce physical abnormalities, -:more likely than nonusers to miscarry, deliver prematurely, or stillborns - some infants exposed to opioid drugs) show normal developmental progress by age 2 -indifferent parenting +other social & environmental risk factors, may be most likely contributor to poor progress -boys may be especially vulnerable to effects of maternal prenatal drug abuse -Cocaine known to constrict blood vessels of both mother & fetus, elevating fetal blood pressure, hampering flow of nutrients and oxygen across placenta - crack and coke babies often miscarried or born prematurely -often display tremors, sleep disturbances, sluggish inattention to environment, tendency to become extremely irritable when aroused -linked to developmental deficits: lower IQ scores , impaired visual-spatial abilities problems w/ skills critical to language development-auditory attention ,comprehension and verbal expression -prenatal and postnatal environment influence severity of cocaine-related developmental deficits -maternal distress shown to contribute to poor fetal growth over and above contributions made by prenatal exposure to cocaine -unpleasant demeanour many cocaine babies display interferes w/ emotional bonding normally occurs b/w infants and caregivers -failed to establish secure emotional tietoprimary caregivers in first year -seem to derive less joy from learning than nonexposed infants do Environmental Hazards -include chemicals in environment that pregnant woman cannot control , may not even be aware of. Radiation. -atomic blasts of 1945 in Japan , teratogenic effects of radiation -Not one pregnant woman within 0.8 krn of explosions gave birth to live child. -75 % pregnant women within 2 krn seriously handicapped children who soon died, -no one knows exactly how much radiation takes to harm an embryo or fetus, -routinely advised to avoid X-rays, particularly of pelvis and abdomen Chemicals and Pollutants - everyday potentially toxic substances : organic dyes , colouring agents, food additives, artificial sweeteners, pesticides, and cosmetic products - risks associated w/ large number of common chemical additives and treatments remain to be determined. - pollutants in air and water. - may be exposed to concentrations of lead, zinc, or mercury, or antimony discharged into air or water - known to impair physical health and mental abilities of adults and children and have teratogenic effects - PCBs (polychlorinated biphenyls), outlawed but once widely used in plastics and carbon paper - low-level exposure to PCBs, resulting from mothers eating contaminated fish from Lake Michigan, make newborns smaller on average , less responsive and neurologically mature than babies - age 4, children still performed poorly on tests of short-term , memory and verbal reasoning ability, - associated w/ difficulty maintaining attention & slower reaction times - children least proficient at task those exposed to high levels of PCB in utero and through breast feeding father's exposure to environmental toxins can affect children - prolonged exposure to radiation, anesthetic gases, and other toxic chemicals can damage father's chromosomes, increasing likelihood of child being miscarried/ having genetic defects 1) environmental toxins can affect reproductive system of either parent -(2) both mothers and fathers should limit exposure to substances to known teratogens. Maternal Characteristics The Mother's Diet - pregnant women often advised to eat healthy, high-protein, high-calorie diet -gain about 1.0 to 2.0 kg during first three months of pregnancy -about 0.5 kg a week thereafter, total increase of about 11.0 to 14.0 kg - Severe malnutrition, occurs during periods of famine, stunts prenatal growth and produces small, underweight babies - first trimester, malnutrition disrupt formation of spinal cord and induce miscarriages. - third trimester, likely to result in low-birth-weight babies w/ small heads who wont survive first year - fewer brain cells and lower brain weights - sometimes show cognitive deficits later in childhood. - babies whose diets remain inadequate after birth often apathetic and quick to become irritated when aroused - Canada, poor women at risk for poor nutrition - nutritional supplement programs have established in some areas - Montreal Diet Dispensary Program initiated 1960s to promote positive pregnancy outcomes among socially disadvantaged urban women - Adding small amounts of magnesium Improves functioning of placenta , reduces incidence of many birth complications - fetus need iodine to ensure normal thyroid functioning. - lack of iodinecongenital hypothyroidismsometimes known as cretinism, disorder leads to irreversible mental retardation - diets rich in folic acid, B-complex vitamin found in fresh fruits, beans, li
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