CHAPTER 4 PRENATAL DEVELOPMENT AND BIRTH Learning Objectives How does development unfold during the prenatal period from conception until the time of birth? What are the developmental milestones of prenatal development? Prenatal Development: Conception Conception The union of the mature ovum and a sperm The genetic material of the cells unite to form a zygote Prenatal Development: Infertility Infertility After a year of trying to get pregnant, conception does not occur Assisted reproduction technologies (ARTs) are used to increase fertility Artificial insemination Sperm injected into a woman?s uterus In vitro fertilization (IVF) Eggs and sperm combined and then placed in a woman?s uterus Stages of Prenatal Development: Germinal Period Lasts approximately 2 weeks Zygote divides through mitosis and forms a blastocyst that implants into the blood vessels of the uterine wall Only about half of fertilized ova implant successfully Between 15-20% of recognized pregnancies terminate in miscarriage As many as 50% of unrecognized pregnancies are estimated to terminate with miscarriage, probably due to genetic defects Stages of Prenatal Development: Embryonic Period From the 3rd week to the 8th week after conception Organogenesis Formation of every major organ Brain and spinal cord, heart, facial features, limbs Layers of the blastocyst differentiate Sexual differentiation Stages of Prenatal Development: Embryonic Period Differentiation of the blastocyst during the embryonic period Outer layer becomes the amnion and chorion Amnion - membrane that fills with fluid that cushions and protects the embryo Chorion ? membrane that surrounds the amnion and eventually becomes the lining of the placenta Placenta ? tissue connected to the embryo by the umbilical cord Placenta and umbilical cord ? embryo receives oxygen and nutrients and eliminates carbon dioxide and metabolic wastes into the mother?s bloodstream Stages of Prenatal Development: Embryonic Period Differentiation of the blastocyst during the embryonic period Cells in interior of blastocyst become the ectoderm, mesoderm, and endoderm Ectoderm ? evolves into the central nervous sytem Mesoderm ? evolves into muscle tissue, cartilage, bone, heart, arteries, kidneys, gonads Endoderm ? gastrointestinal tract, lungs, bladder Stages of Prenatal Development: Embryonic Period Neural tube defects during the embryonic period In approximately 1 of 1,000 pregnancies, the neural tube fails to close completely Spina bifida ? part of the spinal cord not fully encased in the protective covering of the spinal cord Anencephaly ? the top of the neural tube does not close, and the main portion of the brain above the brain stem does not develop Neural tube defects occur 25-29 days after conception More common when the mother is deficient in folic acid Stages of Prenatal Development: Embryonic Period Sexual differentiation during the embryonic period Undifferentiated tissue becomes ovaries or testes In a genetic male, a gene on the Y chromosome directs construction of testes Embryonic testes secrete testosterone that stimulates development of the male internal reproductive system and a hormone that inhibits the development of a female internal reproductive system In a genetic female, ovaries form In the absence of hormones, the embryo develops the internal reproductive system of a female Stages of Prenatal Development: Fetal Period Lasts from the 9th week of pregnancy until birth Cells proliferate, migrate, and differentiate Differentiation of cells occurs according to where cells migrate Organ systems continue to grow and begin to function Sex organs appear during 3rd month of pregnancy Age of viability reached at about 23 weeks When survival is possible if the brain and respiratory system are sufficiently developed Weight gain Organized and adaptive behaviors develop Patterns of heart rate, activity level Learning Objectives How and when do various teratogens affect the developing fetus? How can you summarize the effects of teratogens during the prenatal period? How do maternal age, emotional state, and nutrition affect prenatal and neonatal development? What about the father?s state - can this influence development? Prenatal Environment Reciprocal influences Transactions between the developing organism and its physical and social environments Events of the prenatal period have lifelong effects on physical health and mental development Transactions between the organism and its environment begin at conception Caption: The critical periods of prenatal development Teratogens Any disease, drug, or environmental agent that can harm a developing organism Generalizations about the effects of teratogens Critical period ? effects are worst during the critical period when an organ system grows most rapidly Dosage and duration ? the greater the level of exposure and the longer the exposure, the more likely is serious damage Genetic makeup ? susceptibility to harm influenced by the organism?s and its mother?s genetic makeup Environment ? effects depend upon the quality of both the prenatal and the postnatal environments Continued on next page. Caption: Characteristic features of a child with fetal alcohol syndrome (FAS) Illustrations of the Principles of Teratology - Drugs Thalidomide ? critical periods for different deformities Missing or deformed limbs; deformed eyes, ears, nose, heart; missing ears Tobacco ? smoking restricts blood flow to the fetus and reduces levels of growth factors, oxygen, and nutrients that reach the fetus Associated with higher rates of miscarriage; slower prenatal growth; increased risk for prematurity, low birth weight, cleft lips and palate; increased risk of SIDS Illustrations of the Principles of Teratology ? Drugs Alcohol Readily crosses the placenta to affect fetal development by disrupting the normal process of neuronal migration Fetal alcohol syndrome (FAS) ? most severe FAS children have a smaller head and distinctive facial abnormalities; FAS children are smaller and lag in physical growth compared to age-mates Central nervous system damage Illustrations of the Principles of Teratology- Alcohol Some children experience milder alcohol-related effects as a result of prenatal exposure to alcohol Fetal alcohol effects or alcohol-related neurodevelopmental disorder Not all features of FAS but have physical, behavioral, or cognitive problems, or a combination of problems Illustrations of the Principles of Teratology- Alcohol The effects of alcohol Women who consumer larger quantities are at greater risk for children with alcohol-related complications Binge-drinking has more negative effects than consuming the same number of drinks across multiple occasions The effects of alcohol depend upon which systems are developing at the time of exposure 1st trimester ? facial abnormalities 2nd and 3rd trimesters ? growth and brain development are stunted Illustrations of the Principles of Teratology- Alcohol The effects of alcohol Depend upon the woman?s physiology ? how efficiently she metabolizes alcohol and how much is transmitted to the fetus Depend upon co-occurrence of other factors, such as use of cigarettes and other drugs, adequacy of prenatal care Depend upon the embryo?s genetic makeup and physical condition and associated ability to resist and recover from damage May depend upon direct and indirect paternal factors, such as his genetic makeup or quality of parenting Illustrations of the Principles of Teratology- Drugs Cocaine can cause spontaneous abortion, premature detachment of the placenta, or fetal stroke Cocaine contributes to fetal malnourishment, retarded growth, and low birth weight A small proportion of cocaine-exposed infants experience withdrawal-like symptoms at birth Cocaine-exposed infants show deficits on measures of information processing and sensory motor skills during their first year Most problems caused by prenatal cocaine exposure do not persist into childhood Continued on next page. Illustrations of the Principles of Teratogens - Diseases Rubella (German measles) ? associated with blindness, deafness, heart defects, and mental retardation in exposed infants Most dangerous during the 1st trimester Damage to the central nervous system, eyes, and heart is most likely during the first 8 weeks of pregnancy Deafness is likely if the woman contracts rubella in weeks 6 to 13 of the pregnancy Illustrations of the Principles of Teratogens - Diseases Diabetes Gestational diabetes arises during the pregnancy and results from elevated blood glucose levels Increased risk of prematurity, stillbirth or miscarriage, immature lung development, and large fetal size Syphilis ? sexually transmitted infection Can cause stillbirth or miscarriage Exposed infants may have blindness, deafness, heart problems, or brain damage Most damaging in the middle and later stages of pregnancy Illustrations of the Principles of Teratogens - Diseases Acquired immunodeficiency syndrome (AIDS) is caused by the human immunodeficiency virus (HIV). HIV can be transmitted Prenatally, if the virus passes through the placenta Perinatally, by exposure to blood during birth Postnatally, by breast-feeding If HIV-infected pregnant women are not treated, approximately 15-35% of infants will be infected Illustrations of the Principles of Teratogens ? Environmental Hazards Radiation Doses of radiation used in x-rays and cancer treatments are capable of causing mutations, spontaneous abortions, and birth defects Pollutants Adverse effects are associated with prenatal exposure to air pollution, cigarette smoke, lead, and/or mercury The Mother?s State ? Age Very young mothers have higher-than-normal rates of birth complications, premature delivery, and/or stillbirth Inadequate prenatal care, alcohol use Older women are more likely to experience trouble getting pregnant and have an increased risk of having miscarriage, stillbirth, or low-birth-weight infants Greater chance of multiple pregnancy, which has increased risk of fetal mortality The Mother?s State ? Race/Ethnicity Non-Hispanic black women have fetal mortality rates that are more than twice the rates experienced by other women Non-Hispanic black mothers are more susceptible to premature labor Reasons for disparity are not completely understood, but include poorer preconception health of the mother and less prenatal care The Mother?s State ? Emotional Condition If prolonged and severe emotional stress and anxiety are experienced during pregnancy, consequences may include Faster and more irregular fetal heart rate, stunted prenatal growth, premature birth, birth complications Infants whose mothers were highly stressed during pregnancy Tend to be smaller, more active, more irritable, more prone to crying, and may experience delays in cognitive development Also associated with increased risk of developing schizophrenia The Mother?s State ? Nutritional Condition Doctors now recommend a well-balanced diet with about 300 additional calories per day, with total weight gain of 25-35 pounds for normal-weight women Depending upon when it occurs, malnutrition can result in stillbirths, neural tube defects, stunted growth, and cognitive deficits in infancy and childhood Folate-enriched cereal products are associated with a decrease in the incidence of neural tube defects Prenatal vitamins are recommended The Father?s State Father?s age Children born to teenage fathers have increased risk of birth complications Children born to older fathers have elevated risk of congenital heart defects, neural tube defects, and kidney problems Likelihood of Down syndrome is greater when both father and mother are older Advanced paternal age (50 and older) is a risk factor for schizophrenia Caption: The three stages of labor: Stage 1: (a) contractions of the uterus cause dilation and effacement of the cervix. (b) transition is reached when the frequency and strength of the contractions are at their peak and the cervix opens completely. Stage 2: ( c) the mother pushes with each contraction, forcing the baby down the birth canal, and the head appears. (d) Near the end of Stage 2, the shoulders emerge and are followed quickly by the rest of the baby?s body. Stage 3: (e) with a few final pushes, the placenta is delivered. The Father?s State Research limited except for genetic contribution Father?s age can also be influential Over 35: increased number miscarriages, heart defects, Down syndrome Over 50: higher risk for schizophrenia Exposure to environmental toxins Radiation, anesthetic gases, pesticides Damage to genetic material in sperm Learning Objectives What is the typical perinatal environment like? What hazards can occur during the birth process? What is the birth experience like from the mother?s and father?s perspectives, and from different cultural perspectives? The Perinatal Environment Modern-day birthing practices Medical setting and use of technology in homelike setting Parents want greater flexibility and control, especially control over who will assist with the delivery Presence of supportive people in the delivery room The Perinatal Environment - Childbirth Childbirth is a three-stage process First stage begins with regular uterine contractions and ends when the cervix is fully dilated (10 centimeters) Second stage is delivery, which begins as the fetus?s head moves through the cervix into the vagina and ends when the baby emerges Third stage is delivery of the placenta The Perinatal Environment: Possible Hazards Anoxia ? shortage of oxygen Anoxia is dangerous because brain cells die if they are starved of oxygen for more than a few minutes Severe anoxia can cause poor reflexes, seizures, heart rate irregularities, breathing difficulties, memory impairment, increased risk of learning or intellectual disabilities or speech difficulties, or cerebral palsy The Perinatal Environment: Complicated Delivery If assistance with delivery is necessary, forceps or vacuum extraction (suction) may be used Cesarean section is an alternative to normal vaginal delivery Used when the baby is too large or the mother is too small, the fetus is out of position, when the placenta prematurely separates from the uterus, or fetal monitoring reveals that a birth complication is likely The Perinatal Environment: Complicated Delivery - Cesarean In 2007, 32% of U.S. births were Cesarean Many Cesareans may be unnecessary Reduced liability and more revenue for the obstetrician Choose a second Cesarean rather than attempting vaginal birth Preference for scheduled birth For optimal outcome for infants, elective C-sections should be performed at 39-40 weeks The Perinatal Environment: Complicated Delivery - Medications Laboring women may be given Analgesics and anesthetics to reduce pain Sedatives for relaxation Stimulants to induce or intensify uterine contractions Sedatives can cross the placenta to the infant, and large doses can make the baby sluggish, irritable, difficult to feed or cuddle, and smile infrequently The Mother?s Experience Birth stories are unique Most women report pain and anxiety, and 77% felt the experience was positive Factors that influence the mother?s birth experience Psychological factors such as her attitude and knowledge, sense of control, and social support The Mother?s Experience The experience of childbearing is influenced by its cultural context The desirability of having children Practices and beliefs about pregnancy and delivery In highly industrialized Western societies, childbirth is medicalized The Mother?s Experience Baby blues ? 60% of new mothers report a relatively mild, quickly resolved state Tearful, moody, irritable, anxious, depressed Postpartum depression ? 1 in 10 new mothers experience a longer-lasting clinical depression Most affected women have histories of depression Additional life stresses and lack of social support increase the risk The Mother?s Experience ? Postpartum Depression Research suggests that maternal postpartum depression may affect children?s development Less secure attachment Violent behavior Predisposition to later depression Results from maternal behavior that is unresponsive, possibly hostile, toward the baby; tired, distracted, not fully engaged with the infant Sibling Adjustment ?Transition to siblinghood? Quality of the microsystem Example: strong father-child relationship Exosystem factors Example: parents with strong support less stressed or tired The child?s age, gender, and personality affect how the child responds to and adjusts to a new sibling Children under age 2 do not show the same disruption of mother-child attachment that often occurs when older children acquire a new sibling The Father?s Experience Fathers experience both positive and negative emotions May experience couvade Physiological symptoms associated with pregnancy Possibly experience symptoms of postpartum depression Typically experience postpartum decline in marital satisfaction The Father?s Experience Accepted, expected in delivery rooms Attend prenatal classes with wife Experience described as a significant event Anxiety, stress common during delivery Relief, pride, joy when baby is born Sometimes depression following birth Fathers also need support Disappointed if sex does not resume soon Learning Objectives What are the advantages of breast-feeding? Are there disadvantages of breast-feeding? How can at-risk newborns be identified? What treatments are available to optimize development of at-risk babies? To what extent are the effects of the prenatal and perinatal environments long lasting? What factors influence whether effects are lasting? The Neonatal Environment Ideas about parenting and infant care are culturally constructed Brazelton Neonatal Behavioral Assessment Newborn assessment technique that assesses infant reflexes and infant responses Used to teach parents to understand and appreciate their infants The Neonatal Environment Breast or bottle? All major health organizations advocate for exclusive breast-feeding for the first 6 months of life Health benefits include fewer ear infections and respiratory tract problems, stronger lung function, and positive effects on immune system functioning and weight gain The Neonatal Environment Identifying at-risk newborns Newborns are routinely screened with the Apgar test, which is a quick assessment of Heart rate Respiration Color Muscle tone Reflexes The Neonatal Environment: Identifying At-Risk Newborns Low-birth-weight infants may be born prematurely or to term but ?small for gestational age? Prematurity is the leading cause of infant mortality Low-birth-weight (LBW) infants are born weighing less than 2,500 grams or 5.5 pounds Extremely LBW infants are born weighing less than 1,000 grams or 2 pounds, 3 ounces Micropreemie infants are born weighing less than 800 grams or 1.75 pounds The Neonatal Environment: Identifying At-Risk Newborns Low birth weight is associated with Low socioeconomic status Ethnicity: African-American mothers are twice as likely to experience premature delivery and LBW Smoking Stress Multiple births The Neonatal Environment: Identifying At-Risk Newborns LBW and extremely LBW children at risk for Neuro-behavioral problems, including blindness, deafness, cerebral palsy, poor academic achievement, and autism Respiratory problems as a consequence of insufficient surfactant Substance that prevents air sacs of the lungs from sticking together The Neonatal Environment: Identifying At-Risk Newborns Interventions for LBW infants include surfactant therapy, breast-feeding, kangaroo care (skin-to-skin contact), and massage therapy Long-term outcomes for LBW infants depend upon Their biological condition, specifically their health and neurological condition The quality of their postnatal environment Early intervention programs help parents learn to provide a growth-enhancing home environment Risk and Resilience Some infants who are exposed to and affected by risks recover from their deficiencies The results of Werner?s 40-year-long Kauai longitudinal study revealed that The effects of prenatal and perinatal complications decrease over time The outcomes of early risk depend on the quality of the postnatal environment The study also revealed protective factors Personal resources Supportive postnatal environment
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