chapter 4 prenatal development and birth. black hawk college chapter 42

Chapter 4

Prenatal Development

and Birth

Black Hawk College Chapter 4 2

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The Course of Prenatal Development

• The Germinal Period

• The Embryonic Period

• The Fetal Period


The Germinal Period• It is the period that occurs the first 2 weeks

after conception.• By about 1 week after conception, the

zygote is composed of 100 to 150 cells.• This period includes the creation of the

zygote, continued cell division, and attachment of the zygote to the uterine wall.

• Implantation, or attachment to the uterine wall, occurs about 10 days after conception.


The Differentiation of Cells

• The Blastocyst - the inner layer of cells that develops during the germinal period and later becomes the embryo

• The Trophoblast - the outer layer of cells that develops during the germinal period and later provides nutrition and support for the embryo


The Embryonic Period• The period that occurs from 2 to

8 weeks after conception• The rate of cell differentiation

intensifies, support systems for the cells form, and organs appear

• The name of the mass of cells now changes from zygote to embryo


Cell Layers of the Embryo

• Endoderm - inner layer; develops into the digestive and respiratory systems

• Ectoderm - outermost layer; becomes the nervous system, sensory receptors (ears, nose, eyes), and skin parts (hair and nails)

• Mesoderm - middle layer; becomes the circulatory system, bones, muscles, excretory system, and reproductive system


Prenatal Life-Support Systems• The Placenta - consists of a disk-shaped group of

tissues in which small blood vessels from the mother and the offspring intertwine but do not join– Very small molecules (oxygen, water, salt, food

from mother’s blood, carbon dioxide) pass back and forth between mother and infant.

– Large molecules (red blood cells, hormones, most bacteria) cannot pass through the placental barrier.

• The Umbilical Cord - contains two arteries and one vein, that connects the baby to the placenta

• The Amnion - a bag or envelope that contains a clear fluid in which the developing embryo floats


Important Embryonic Developments

• Third Week - Neural tube develops• 21 Days - Eyes begin to appear• 24 Days - Heart cells begin to differentiate• Fourth Week - First appearance of the

urogenital system, arm and leg buds appear, chambers of the heart take shape, blood vessels surface

• Fifth to Eighth Week - Arms and legs differentiate further, face starts to form, intestinal tract develops, facial structures fuse

• 8 Weeks - organisms weighs 1/30 ounce, 1 inch long


Definition of Organogenesis

• The process of organ formation that takes place during the first 2 months of prenatal development

The Fetal Period• The period that begins 2 months after conception and lasts, on average, 7 months• Significant time periods:

– Three months after conception– The end of the fourth month– The end of the fifth month– The end of the sixth month– The end of the seventh month– The eighth and ninth months


Three Months after Conception

• The fetus is 3 in. long and weighs 1 oz.• The fetus becomes active, moving its

arms, legs, head, and opening and closing its mouth.

• The face, forehead, eyelids, nose, chin, upper arms, lower arms, hands, and lower limbs are all distinguishable.

• The genitals can be distinguished as male or female.


The End of the Fourth Month

• The fetus is 6 in. long and weighs 4-7 oz.

• A growth spurt occurs in the body’s lower parts.

• Prenatal reflexes are stronger.• Arm and leg movements can be

felt by the mother for the first time.


The End of the Fifth Month

• The fetus is 12 in. long and weighs close to 1 lb.

• Structures of skin have formed (such as toe and finger nails).

• The fetus is more active, and shows a preference for a particular position in the womb.


The End of the Sixth Month

• The fetus is approximately 14 in. long and weighs about 2 lbs.

• The eyes and eyelids are completely formed.

• A fine layer of hair covers the head.

• A grasping reflex is present.• Irregular breathing movements

occur.


The End of the Seventh Month

• The fetus is 16 in. long and weighs 3 lbs.

• The fetus is adding body fat.

• The fetus is very active.

• Basic breathing begins.


The Eighth and Ninth Months

• The fetus grows longer and gains substantial weight, about another 4 lbs.

• Fatty tissues develop, and the functioning of organ systems, such as heart and kidneys, increases.

• At birth, the average American baby is about 20 in. long and weighs 7 lbs.


Cultural Beliefs about Pregnancy

• Specific actions in pregnancy are often determined by cultural beliefs.

• Two fundamental views of pregnancy:– Pregnancy is a medical condition.– Pregnancy is a natural occurrence.

• It is important for health-care providers to become aware of health practices of various cultural groups, along with their health beliefs about pregnancy and prenatal development.


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Exploring Teratology• Teratology - The field of study that investigates

the causes of birth defects.• Teratogen - Any agent that causes a birth

defect.• Numerous teratogens exist, thus almost every

fetus is exposed to at least some.• Specific teratogens do not usually cause a

specific birth defect.• It may take a long time for the effects of a

teratogen to show up.• Only about half of all potential effects appear at

birth.


Prenatal Sensitivity to Teratogens

• Sensitivity during Organogenesis

• Sensitivity during the Fetal Period


Sensitivity during Organogenesis

• The probability of a structural defect is greatest during organogenesis.

• 15 - 25 days after conception, the brain is most vulnerable.

• 24 - 40 days after conception, the eyes are most vulnerable.

• 20 - 40 days after conception, the heart is most vulnerable.

• 24 - 36 days after conception, the legs are most vulnerable.


Sensitivity during the Fetal Period

• Exposure is less likely to cause anatomical defects.

• Exposure is more likely to stunt growth.

• Exposure is more likely to create problems in organ functioning.


Prescription and Nonprescription Drugs

• Both can have possible effects on the fetus.• A tragic example is with the tranquilizer

thalidomide, prescribed in the early 1960s.– Clearly demonstrated the varying periods of

sensitivity to teratogens through differing outcomes based on when mothers used the drug.

• Mothers do not have to be chronic drug users for the fetus to be harmed.

• Taking the wrong drug at the wrong time is enough to physically handicap offspring for life.


• Antibiotics (streptomycin, tetracycline)

• Some depressants• Certain hormones

(progestin, synthetic estrogen)

• Accutane

Prescription Drugs that Can Function as

Teratogens


• Diet Pills• Aspirin• Caffeine

– A small increase in the risks for spontaneous abortion and low birthweight occurs for pregnant women consuming >150 mg caffeine per day.

– No effects were found for pregnant women who drank decaffeinated coffee.

– FDA recommends either no caffeine or very little.

Nonprescription Drugs that Can Function as

Teratogens


Psychoactive Drugs

• Alcohol

• Nicotine

• Illegal Drugs


• Heavy Drinking

• Moderate Drinking

Alcohol


• Fetal Alcohol Syndrome (FAS) - A cluster of abnormalities that appears in the offspring of mothers who drink alcohol heavily during pregnancy– Facial deformities– Defective limbs, face, and heart– Below average intelligence, with some cases

of mental retardation– Adults with FAS found to have a high

incidence of mental disorders, such as depression or anxiety

Heavy Drinking during Pregnancy


• “Moderate” is defined as 1 to 2 drinks a day.

• Infants were less attentive and alert, with effects still present at 4 years of age.

• One recent study showed that prenatal alcohol exposure was a better predictor of adolescent alcohol use and its negative consequences than was family history of alcohol problems.

Moderate Drinking during Pregnancy


• Fetal and neonatal deaths are higher among smoking mothers.

• There exists a higher incidence of preterm births and lower birthweights.

• Intervention programs designed to get pregnant women to stop smoking can reduce some of smoking’s negative effects, especially by raising birthweights.

Nicotine


The Research on Smoking during Pregnancy

• Studies have shown urine samples of newborns with smoking mothers had substantial amounts of one of the strongest carcinogens in tobacco smoke (NNK).

• Another study showed prenatal exposure to nicotine was related to poorer language and cognitive skills at 4 years of age.

• Respiratory problems and SIDS are more common among the offspring of mothers who smoked during pregnancy.


• Cocaine

• Marijuana

• Heroin

Illegal Drugs


• The most consistent finding is that cocaine exposure during prenatal development is associated with reduced birthweight, length, and head circumference.

• A recent study associated cocaine exposure with impaired motor development at 2 years of age.

• Fetal cocaine exposure is also linked with impaired information processing (poor attentional skills through 5 years of age; impaired processing of auditory information after birth).

Cocaine Use during Pregnancy


• Research findings must be interpreted with caution due to the presence of other factors in the lives of pregnant women who use cocaine:– Poverty– Malnutrition– Other substance abuse:cigarettes,

marijuana, alcohol, amphetamines

Other Related Influences


• Associated with increased tremors and startles among newborns

• Associated with poorer verbal and memory development at 4 years of age

Marijuana Use during Pregnancy


• Young infants are addicted and show withdrawal symptoms characteristic of opiate abstinence:– Tremors– Irritability– Abnormal crying– Disturbed sleep– Impaired motor control

• Behavioral problems are still present at the first birthday.

• Attention deficits may appear later in development.

Heroin Use during Pregnancy


Environmental Hazards

• Radiation: nuclear environments, X-rays, computer monitors

• Chemicals: carbon monoxide, mercury, lead, pesticides, PCBs

• Heat: saunas, hot tubs


• Can cause gene mutation• Can cause chromosomal

abnormalities• X-rays can effect the

developing embryo most during the first several weeks after conception.

Findings on Radiation Exposure


• Early exposure to lead affects children’s mental development.

• Women who ate PCB-polluted fish were more likely to have smaller, preterm infants who reacted slowly to stimuli.

• Prenatal exposure to PCBs has also been associated with problems in visual discrimination and short-term memory in 4-year-old children.

Findings on Hazardous Chemicals


• Prolonged exposure to heat in saunas or hot tubs that raises the mother’s body temperature creates a fever that endangers the fetus.

• The high temperature may interfere with cell division and may cause birth defects or even fetal death.

Effects of Exposure to High

Temperatures


• Infectious Diseases• Nutrition• Emotional States and

Stress• Maternal Age

Other Maternal Factors


• Rubella

• Syphilis

• Genital Herpes

• AIDS

Infectious Diseases


• Also known as German Measles, the greatest damage occurs when mothers contract it in the 3rd and 4th weeks of pregnancy, although infection during the 2nd month is also damaging.

• A rubella outbreak in the mid 1960s resulted in 30,000 prenatal and neonatal deaths.

• It also caused more than 20,000 infants to be affected, displaying mental retardation, blindness, deafness, and heart problems.

Rubella


• Syphilis is a sexually transmitted disease.• It is more damaging in later prenatal

development, 4 months or more after conception.

• It damages organs after they are formed, including– eye lesions (which can cause

blindness)– skin lesions

• If it is present at birth it can cause problems with the central nervous system and gastrointestinal tract.

Syphilis


• Newborns contract the virus when they are delivered through the birth canal of a mother with genital herpes.

• One-third of babies delivered through an infected birth canal die.

• One-fourth of babies delivered through an infected birth canal become brain damaged.

• If an active case of genital herpes is detected close to a woman’s due date, a cesarean section can be performed to keep the newborn safe.

Genital Herpes


• AIDS is a sexually transmitted disease which destroys the body’s immune system.

• A mother can infect her offspring in three ways:– during gestation across the placenta– during delivery through contact with maternal body

fluids– postpartum through breast feeding

• Babies born to infected mothers can be– infected and symptomatic– infected but asymptomatic (with the possibility of

developing symptoms up until 15 months of age)– not infected at all

AIDS


• A developing fetus depends completely on its mother for nutrition, which comes from her blood.

• Important factors of nutritional status are– total number of calories– levels of protein, vitamins, and minerals– folic acid

• A folic acid deficiency is linked with neural tube defects, such as spina bifida.

Nutrition


• Effects on Pregnancy

• Effects on Labor and Delivery

Emotional States and Stress


• Mother’s stress can be transmitted to the fetus.

• When a pregnant woman experiences intense fears, anxieties, and other emotions, physiological changes occur.– respiration– glandular secretions, such as

adrenaline• These affect the fetus through, for

example, restricting blood flow to the uterine area depriving the fetus of adequate oxygen.

Effects of Stress on Pregnancy


Effects of Stress on Labor and Delivery• A mother’s emotional state during pregnancy

can influence the birth process.• An emotionally distraught mother may have

irregular contractions and a more difficult labor.• This can lead to irregularities in the baby’s

oxygen supply or irregularities after birth.• Research has found women under stress are

four times as likely to deliver their babies prematurely.

• Research has found that pregnant women who are optimists have less adverse birth outcomes.


Maternal Age

• Adolescence

• The Thirties and Beyond


Adolescence• Infants born to adolescents are often

premature.• The mortality rate of infants born to

adolescent mothers is double that of infants born to mothers in their twenties.

• May be due to– immature reproductive systems– poor nutrition– lack of prenatal care– low SES


• The risk of Down Syndrome increases after the mother reaches age 30.

• Women have more difficulty getting pregnant after the age of 30.

• As women remain active, exercise regularly, and are careful about their nutrition, their reproductive systems may remain healthier at older ages.

The Thirties and Beyond


• Men’s exposure to lead, radiation, certain pesticides, and petrochemicals may cause abnormalities in sperm that lead to miscarriage or disease.

• When fathers have a diet low in vitamin C, their offspring have a higher risk of birth defects and cancer.

• Early findings point to a connection between cocaine use in fathers and birth defects.

• Fathers’ smoking during pregnancy may lead to lower birthweight and potential for their offspring developing cancer.

• Older fathers may place their offspring at risk for certain birth defects, such as Down syndrome and dwarfism.

Paternal Factors


• Usually involves a package of medical care services in a defined schedule of visits

• Often includes educational, social, and nutritional services

• Includes screening for conditions that can affect the baby or mother

• Is extremely valuable, especially for first-time mothers

• Is very important for women in poverty because it links them with other social services

• Can motivate women to have positive attitudes toward pregnancy

• Not all women have access to or seek out adequate prenatal care

Prenatal Care


• In most pregnancies, prenatal development does not go awry and development occurs along a positive path.

• Prospective parents should be careful to avoid the vulnerabilities to fetal development.

Positive Prenatal Development


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Exploring the Birth Process

• Stages of Birth• The Fetus/Newborn

Transition• Childbirth Strategies


The First Stage of Birth• This is the longest of the three

stages, lasting an average of 12-24 hours.

• Uterine contractions are 15-20 minutes apart and last up to 1 minute.

• Contractions cause cervix to stretch and open.

• Contractions get closer together as the stage progresses.

• By the end of this stage the cervix is dilated to about 4 inches.


The Second Stage of Birth

• This stage begins when the baby’s head starts to move through the cervix and the birth canal.

• It terminates when the baby completely emerges from the mother’s body.

• This stage lasts about one and a half hours, and involves the mother bearing down to push the baby out.

• Contractions come about every minute and last about a minute.


The Third Stage of Birth

• This stage is called “afterbirth” and lasts only minutes.

• It involves the detachment and expulsion of the placenta, umbilical cord, and other membranes.


The Fetus/Newborn Transition

• Being born involves considerable stress for the baby.

• Anoxia (the condition in which the fetus/newborn has an insufficient supply of oxygen) can cause brain damage, and is a concern if delivery takes too long.

• Large quantities of adrenaline and noradrendaline are secreted to protect the fetus in the event of oxygen deficiency.

• After the umbilical cord is cut, 25 million air sacs in the lungs must fill with air.

• The newborn’s bloodstream is redirected through the lungs and to all parts of the body.

• The baby is born with a protective covering of skin grease called vernix caseosa which is cleaned off.


Childbirth Strategies

• Childbirth Setting and Attendants

• Methods of Delivery


Childbirth Setting and Attendants

• Ninety-nine percent of all births in the U.S. take place in hospitals, and 90% are attended by physicians.

• Relatively new birthing rooms approximate a home setting, yet allow for medical intervention if necessary or desired.

• About 6% of women deliver a baby with the help of a midwife, most of whom are nurses specially trained in delivering babies.

• In many other countries, babies are more likely to be born at home, and women are much more likely to choose a midwife than a physician.

• A doula is a caregiver who provides continuous physical, emotional, and educational support before, during, and after birth.


Methods of Delivery

• Medicated

• Natural

• Prepared

• Cesarean


Medicated Childbirth• The American Academy of Pediatrics

recommends the least possible medication during delivery.

• Three basic kinds of drugs used for labor:– Analgesia: used to relieve pain

(tranquilizers, barbiturates, narcotics)– Anesthesia: blocks sensation in an area of

the body, or blocks consciousness (epidural)

– Oxytocics: synthetic hormones that stimulate contractions (Pitocin)

• Individuals differ as to how drugs affect them.


Natural Childbirth• Developed by an English obstetrician to

reduce the mother’s pain by decreasing her fear through education about childbirth, and by teaching her to use breathing methods and relaxation techniques during delivery.

• It considers the doctor’s relationship with the mother as an important aspect of reducing her perception of pain, and he or she should be present during active labor to provide reassurance.


Prepared Childbirth• Developed by French obstetrician,

Ferdinand Lamaze, and is similar to natural childbirth with the addition of a special breathing technique to control pushing in the final stages of labor.

• It also includes a more detailed anatomy and physiology course.

• Other prepared childbirth techniques have been developed, combining aspects from both of these methods and emphasizing fathers as labor coaches.


Cesarean Delivery• The baby is removed from the mother’s

uterus through an incision made in her abdomen.

• Usually performed if the baby is in a breech position, causing the baby’s buttocks to emerge from the vagina first.

• Also used if:– the baby is lying crosswise in the uterus– the baby’s head is too large to fit through

the pelvis– the baby develops complications– the mother is bleeding vaginally


Preterm Infants and Age-Weight

Considerations• Preterm and Low-

Birthweight Infants

• Long-Term Outcomes for Low-Birthweight Infants


Preterm and Low-Birthweight Infants

• A preterm infant is one who is born prior to 38 weeks after conception.

• A low-birthweight infant is born after a regular gestation period of 38-42 weeks, but weighs less than 5 and 1/2 pounds.

• Both are considered high-risk infants.• A short gestation period does not

necessarily harm an infant, and neurological development continues after birth on the same timetable.

• Premature infants with a precariously low birthweight are at high risk for survival.


Long-Term Outcomes for Low-Birthweight

Infants• Most low-birthweight infants are normal

and healthy; as a group they have more health and developmental problems.

• The number and severity of problems increase as birthweight decreases.

• With the improved survival rates of such infants come increases in severe brain damage.

• Lower brain weight is associated with greater likelihood of brain injury.


Long-Term Outcomes for Low-Birthweight

Infants (cont’d)• Low-birthweight infants are also more

likely to have lung or liver diseases.• School age children who were low-

birthweight babies are more likely to have learning disabilities, attention deficit disorder, or breathing problems like asthma.

• Children born very low in birthweight have more learning problems and lower levels of achievement in reading and math than moderately low-birthweight children.


Measures of Neonatal Health and

Responsiveness• The Apgar Scale

• The Brazelton Neonatal Behavioral Assessment Scale


The Apgar Scale• A method widely used to assess the health of

newborns at 1 and 5 minutes after birth.• It evaluates infants’

– heart rate– respiratory effort– muscle tone– body color– reflex irritability

• Obstetrician or nurse assesses the newborn and gives a score of 0, 1, or 2 on each item.

• A score of 7-10 is good, 5 indicates possible developmental difficulties, 3 or below signals an emergency.


The Brazelton Neonatal Behavioral Assessment

Scale• Performed within 24-36 hours after birth

to evaluate neurological development, reflexes, and reactions to people.

• The newborn is rated on each of 27 items, contributing to four categories: physiological, motoric, state, and interaction.

• Babies are also given global classification such as “worrisome,” “normal,” “superior.”

• Parents are shown the importance of social interaction with their infant, and how to positively respond to their baby.


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What Is the Postpartum Period?

• The period after childbirth or delivery• Woman’s body adjusts, physically and

psychologically, to the process of childbearing.• Lasts about 6 weeks, body returns to near

prepregnant state.• Influenced by what precedes it—method and

circumstances of delivery affect speed of readjustment

• Adjustment and adaptation include:- learning to care for baby - recovering from

childbirth- caring for baby - learning to feel

good as mother- father caring for wife - father learning to

care for baby


Physical Adjustments• Involution is the process by which the uterus returns

to its prepregnant size, 5-6 weeks after birth.• Nursing the baby helps contract the uterus rapidly.• Menstruation begins 4-8 weeks after delivery if she is

not breast-feeding.• Breast-feeding causes a delay in menstruation for

several months, but ovulation can still occur.• Physicians usually recommend refraining from sexual

intercourse for approximately 6 weeks following birth.• Exercise is recommended for the postpartum period,

as are relaxation techniques to relax and refresh the mother.


Emotional and Psychological Adjustments

• Emotional fluctuations are common for the mother in the postpartum period and can be caused by– hormonal changes– fatigue– inexperience/lack of confidence with the baby– the extensive time and demands of caregiving

• Mothers may benefit from professional help in dealing with their problems if difficulties persist.

• Fathers undergo postpartum adjustment as well, in caregiving and with concerns that the baby comes first and gets all the mother’s attention.


Bonding• Bonding is the occurrence of close contact,

especially physical, between parents and newborn in the period shortly after birth.

• This is a critical time when an important emotional attachment is formed that provides a foundation for optimal development in years to come.

• Research supports the importance of bonding, but challenges the significance of the first few days of life as a critical period.

• Close contact does bring tremendous pleasure, and can set in motion a climate for improved interaction after the mother and infant leave the hospital.

• Many hospitals offer a “rooming in” arrangement, in which the baby remains in the mother’s room for most of its hospital stay.

chapter 4 prenatal development and birth. black hawk college chapter 42

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