(5) Critical Issues Pertaining to Heredity and Environmental Influences During Prenatal Development

Fertilization (Conception)

is the process of the unison of sperm and ovum to produce a zygote

Zygote

one-celled organism resulting from fertilization

Zygote

Duplicates itself again and again by cell division to produce all the cells that make up a baby

Ovulation

rupture of a mature follicle in either ovary and expulsion of its ovum, occurs about once every 28 days until menopause

Ovum

swept along through one of the fallopian tubes by the cilia, tiny hair cells, toward the uterus, or womb

Sperm

deposited in the vagina, they try to swim through the cervix, the opening of the uterus, and into the fallopian tubes, but only a tiny fraction make it that far

Dizygotic Twins (Fraternal Twins)

are the result of two separate eggs being fertilized by two different sperm to form two unique individuals

Monozygotic Twins (Identical Twins)

twins resulting from the division of a single zygote after fertilization

Genetic & Chromosomal Abnormalities - Incomplete Dominance

pattern of inheritance in which a child receives two different alleles, resulting in partial expression of a trait

Genetic & Chromosomal Abnormalities - Sex-Linked Inheritance

pattern of inheritance in which certain characteristics carried on the X chromosome inherited from the mother are transmitted differently to her male and female offspring

Genetic & Chromosomal Abnormalities - Sex-Linked Inheritance

Males receive only one copy of any gene that happens to be carried on the sex chromosomes, whereas females receive two copies

Sex-Linked Inheritance — Carriers

heterozygote females who carry one “bad” copy of a recessive gene and one “good” one

Sex-Linked Inheritance — Sex-linked Recessive Disorders

more common in males than females red-green color blindness, hemophilia, and Duchenne muscular dystrophy

Genetic & Chromosomal Abnormalities - Sex-Linked Inheritance

Genetic & Chromosomal Abnormalities - Chromosomal Abnormalities

typically occur because of errors in cell division, resulting in an extra or missing chromosome

Chromosomal Abnormalities - XYY Syndrome (Jacob’s Syndrome)

male; tall structure, tendency toward low IQ, especially verbal

Chromosomal Abnormalities - XXX Syndrome (Triple X Syndrome)

female; normal appearance, menstrual irregularities, learning disorders, mental retardation

Chromosomal Abnormalities - XXY (Klinefelter Syndrome)

male; sterility, underdeveloped secondary sex characteristics, small testes, learning disabilities

Chromosomal Abnormalities - XO (Turner Syndrome/ Monosomy X)

female; short stature, webbed neck, impaired spatial abilities, no menstruation, infertility, underdeveloped sex organs

Chromosomal Abnormalities - Fragile X Syndrome

minor-to-severe mental retardation; more severe in males; delayed speech and motor development, hyperactivity; the most common inherited from mental retardation

Chromosomal Abnormalities - Trisomy 21 (Down Syndrome)

characterized by moderate-to-severe mental retardation and by such physical signs as a downward sloping skin fold at the inner corners of the eyes

Chromosomal Abnormalities - Trisomy 18 (Edwards Syndrome)

individuals with trisomy 18 often have slow growth before birth (intrauterine growth retardation) and a low birth weight

Chromosomal Abnormalities - Trisomy 13 (Patau Syndrome)

characterized by cleft lip, cleft palate, cerebral defects, anophthalmia, simian creases, polydactyly, trigger thumbs, and capillary hemangiomata

Gene-Linked Abnormalities - Alpha1 Antitrypsin Deficiency

Enzyme deficiency that can lead to cirrhosis of the liver in early infancy and emphysema and degenerative lung disease in middle age

Gene-Linked Abnormalities - Alpha1 Antitrypsin Deficiency

Alpha Thalassemia

Gene-Linked Abnormalities - Alpha1 Antitrypsin Deficiency

Severe anemia; nearly all affected infants are stillborn or die soon after birth

Gene-Linked Abnormalities - Beta Thalassemia (Cooley’s Anemia)

Severe anemia; usually fatal in adolescence or young adulthood

Gene-Linked Abnormalities - Cystic Fibrosis

Overproduction of mucus, which collects in the lung and digestive tract

Gene-Linked Abnormalities - Duchenne Muscular Dystrophy

Fatal disease usually found in males, marked by muscle weakness; minor mental retardation is common; respiratory failure and death usually occur in young adulthood

Gene-Linked Abnormalities - Hemophilia

Excessive bleeding, usually affecting males; in its most severe form, can lead to crippling arthritis in adulthood

Gene-Linked Abnormalities - Anencephaly

Absence of brain tissues; infants are stillborn or die soon after birth

Gene-Linked Abnormalities - Spina Bifida

Incompletely closed spinal canal, muscle weakness or paralysis and loss of bladder and bowel control

Gene-Linked Abnormalities - Phenylketonuria (PKU)

Metabolic disorder resulting in mental retardation

Gene-Linked Abnormalities - Polycystic Kidney Disease

Infantile form: enlarged kidneys, leading to respiratory problems and congestive heart failure

Gene-Linked Abnormalities - Polycystic Kidney Disease

Adult form: kidney pain, kidney stones, and hypertension resulting in chronic kidney failure

Gene-Linked Abnormalities - Sickle-Cell Anemia

Deformed red blood cells that clog blood vessels, depriving the body of oxygen; symptoms include severe pain, stunted growth, infections, leg ulcers, gallstones, pneumonia, and stroke

Gene-Linked Abnormalities - Tay-Sachs Disease

Degenerative disease of the brain and nerve cells

Genetic Counseling & Testing

Help prospective parents assess their risk of bearing children with genetic or chromosomal defects

Genetic Counseling & Testing

Takes a family history and gives the prospective parents and any biological children physical examinations

Genetic Counseling & Testing

Laboratory investigations of blood, skin, urine, or fingerprints may be performed

Genetic Counseling & Testing

Chromosomes from body tissues may be analyzed and photographed, and the photographs enlarged and arranged according to size and structure on a chart

Karyotype

can show chromosomal abnormalities and can indicate whether a person might transmit genetic defects if a child

Gestation

period of development between conception and birth

Gestation

The normal range of gestation is between 37 and 41 weeks

Gestational Age

usually dated from the first day of an expectant mother’s last menstrual cycle

Pregnancy Test

detects the presence of human chorionic gonadotropin which is produced only by embryos and fetuses

Infertility

inability to conceive a child after 12 months of sexual intercourse without the use of birth control

Stages of Prenatal Development - Germinal Stage (Fertilization to 2 Weeks)

characterized by rapid cell division, blastocyst formation, and implantation in the wall of the uterus

Germinal Stage - Implantation

the attachment of the blastocyst to the uterine wall, occurring at about day 6

Germinal Stage - Blastocyst

a fluid-filled sphere, which floats freely in the uterus until the sixth day after fertilization

Parts of Blastocyst - Amniotic Sac

a fluid-filled membrane that encases the developing embryo, protecting it and giving it room to move and grow

Parts of Blastocyst - Placenta

allows oxygen, nourishment, and wastes to pass between mother and embryo

Parts of Blastocyst - Placenta

It is connected to the embryo by the umbilical cord

Parts of Blastocyst - Placenta

Helps to combat internal infection and gives the unborn child immunity to various diseases

Parts of Blastocyst - Placenta

Produces the hormones that support pregnancy, prepare the mother’s breasts for lactation

Parts of Blastocyst - Placenta

Stimulate the uterine contractions that will expel the baby from the mother’s body

Germinal Stage - Embryonic Disk

a thickened cell mass from which the embryo begins to develop

Layers of Embryonic Disk - Ectoderm (upper layer)

become the outer layer of skin, the nails, hair, teeth, sensory organs, and the nervous system, including the brain and spinal cord

Layers of Embryonic Disk - Endoderm (inner layer)

become the digestive system, liver, pancreas, salivary glands, and respiratory system

Layers of Embryonic Disk - Mesoderm (middle layer)

will develop and differentiate into the inner layer of skin, muscles, skeleton, and excretory and circulatory systems

Stages of Prenatal Development - Embryonic Stage (2 to 8 Weeks)

characterized by rapid growth and development of major body systems and organs

Embryonic Stage - Organogenesis

characterized by rapid growth and development of major body systems and organs

Embryonic Stage - Spontaneous Abortion/ Miscarriage

natural expulsion from the uterus of an embryo that cannot survive outside the womb

Stages of Prenatal Development - Fetal Stage (8 Weeks to Birth)

final stage of gestation, characterized by increased differentiation of body parts and greatly enlarged body size

Fetal Stage - Ultrasound

prenatal medical procedure using high-frequency sound waves to detect the outline of a fetus and its movements, so as to determine whether a pregnancy is progressing normally

Fetal Stage - 12th week of gestation

the fetus swallows and inhales some of the amniotic fluid in which it floats (may stimulate the building senses of taste and smell)

Fetal Stage - 14th week of gestation

olfactory system well developed before birth

Fetal Stage - 26th week of gestation

responses to sound and vibration

Fetal Stage - 33rd week of gestation

orient toward and attend to music

Monitoring Prenatal Development - Prenatal Cell-Free DNA

is extracted from the mother’s blood and tested

Monitoring Prenatal Development - Prenatal Cell-Free DNA

These tests have been shown to be useful for early detection of genetic problems, although they are not definitive

Monitoring Prenatal Development - Amniocentesis

is procedure in which a sample of amniotic fluid is withdrawn for analysis

Monitoring Prenatal Development - Chorionic Villus Sampling

tissue from the membrane surrounding the fetus is removed and analyzed

Monitoring Prenatal Development - Embryoscopy, Fetoscopy

the insertion of tiny viewing scope into the mother’s uterus through the abdominal wall for a direct look at the embryo, can help to diagnose non-chromosomal disorders

Monitoring Prenatal Development - Umbilical Cord Sampling

allows direct access to fetal DNA in the blood vessels of the umbilical cord for the diagnosis

Monitoring Prenatal Development - Ultrasound (Sonogram), Sonoembryology

high-frequency sound waves directed at the mother’s abdomen produce a picture of fetus in uterus

Ultrasound (Sonogram) - Sonoembryology

uses high-frequency transvaginal probes and digital image processing to produce a picture of embryo in uterus

Monitoring Prenatal Development - Preimplantation Genetic Diagnosis

after in vitro fertilization, a sample cell is removed from the blastocyst and analyzed

The Birth Process - Labor

the process of giving birth

The Birth Process - Parturition

the act or or process of giving birth, and it typically begins about 2 weeks before delivery

The Birth Process - Uterine Contraction

begins typically about 266 days after conception

The Birth Process - Braxton-Hicks Contractions

false contractions, when the muscles of the uterus tighten for up to 2 minutes

Stages of Birth - Stage 1: Dilation of the Cervix

The longest, typically lasting 12 to 14 hours for a woman having her first child

Stages of Birth - Stage 1: Dilation of the Cervix

Regular and increasingly frequent uterine contractions: 15 to 20 minutes apart at first

Stages of Birth - Stage 1: Dilation of the Cervix

Toward the end of the first stage, contractions occur every 2 to 5 minutes

Stages of Birth - Stage 2: Descent and Emergence of the Baby

Typically lasts up to an hour or two

Stages of Birth - Stage 2: Descent and Emergence of the Baby

Begins when the baby’s head begins to move through the cervix into the vaginal canal, and it ends when the baby emerges completely from the mother’s body

Stages of Birth - Stage 3: Expulsion of the Placenta

Lasts between 10 minutes and 1 hour

Stages of Birth - Stage 3: Expulsion of the Placenta

The placenta and the remainder of the umbilical cord are expelled from the mother

Delivery Methods - Vaginal Delivery

the usual method of childbirth

Delivery Methods - Cesarean Delivery

used to surgically remove the baby from the uterus through an incision in the mother’s abdomen

Delivery Methods - Natural Childbirth

method of childbirth that seeks to prevent pain by eliminating the mother’s fear through education about the physiology of reproduction and training in breathing and relaxation during delivery

Delivery Methods - Prepared Childbirth

method of childbirth that uses instruction, breathing exercises, and social support to induce controlled physical responses to uterine contractions and reduce fear and pain

Delivery Methods - Lamaze Method (Ferdinand Lamaze)

teaches expectant mothers to work actively with their bodies through controlled breathing where the woman learns to relax her muscles as a conditioned response to the voice of her coach who attends classes with her, takes part in the delivery, and helps with the exercises

Delivery Methods - Leboyer Method (1970’s)

a woman gives birth in a quiet room under low lights to reduce stress, and the newborn is gently massaged to ease crying

Delivery Methods - Michael Odent (French Physician)

submersion of the laboring mother in a soothing pool of water

Delivery Methods - Bradley Method

focus on natural process of birth and instructs women to focus on controlling their pain

Delivery Methods - Doula

an experienced mentor who furnishes emotional support and information for a woman during labor

Breech Position

baby’s buttocks are the first part emerge from the vagina which can cause respiratory problems

Complications of Birth - Low Birth Weight

less than 2,500 grams (5 lbs.) at birth