prenatal development and childbirth

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Prenatal Development and Childbirth

Chapter 3

3


Prenatal Development and Childbirth

• Prenatal Growth and Development

• Prenatal Environmental Influences

• Childbirth

• The Evolving Family


Prenatal Growth and Development• Prenatal development is divided into three

periods:– Germinal: 0 to 2 weeks

– Embryonic: 2 to 8 weeks

– Fetal: 9 to 38 weeks


Prenatal Growth and Development

• Ovulation occurs about 2 weeks after start of menstrual period– The ovum (egg) travels through fallopian

tubes, where fertilization may take place

– If fertilization takes place, a zygote results


Two Ways to Describe the Prenatal Period


Germinal Period

• Time of extremely active cell vision

• Toward end of first week after conception, cells have developed into a blastula, ball of cells around a fluid-filled center

• Cells begin to differentiate to form supportive structures

• Twins may develop during the first few divisions of the zygote

– Monozygotic (identical) twins develop when two identical cells separate and develop into two embryos

– Dizygotic (fraternal) twins develop when two eggs (ova) are released simultaneously and each unites with a different sperm


Ovulation and Fertilization


Embryonic Period

• Beings when implantation is complete

• Some cells form the embryonic disc, from which the child will develop

• Other cells will form supportive structures differentiated into the: – placenta

– umbilical cord

– amniotic sac


The Embryo

• Develops into three distinct layers:

– Ectoderm: outer layer

• Will become skin, sense organs, brain, nervous system

– Mesoderm: middle layer

• Will become muscles, blood, excretory system

– Endoderm: inner layer

• Will become digestive system, lungs, thyroid, thymus, and other organs


The Embryo (continued)

• During the second month, most major body structures develop, except the brain

• Spontaneous abortions (miscarriages) occur primarily during first trimester, usually by 12 or 13 weeks

– Often caused by genetic defects or unsuccessful implantation

– Maternal age, health, nutrition, and exposure to toxic substances, are also risk factors


The Fetal Period

• Lasts from the beginning of third month until birth

• Organs and systems mature and develop, especially the brain and nervous system

• At age 24 weeks, the healthy fetus reaches the age of viability, meaning it has a 50% chance of surviving outside the womb if given high-quality intensive care

• Half of surviving fetuses born at 24 weeks have serious anomalies


Milestones of Development in the Fetal Period

• Week 12– Size: 3 inches long, 1 ounce– Arms, legs, and fingers are developed and can

move– Fingerprints developed– Sexual organs developed– Vocal cords and taste buds formed– Eyes and teeth begin to develop



• Week 16– Size: 5 1/2 inches long, 4 ounces– Heartbeat is stronger and more regular– Lanugo develops and covers the body– Fingernails and toenails developed

• Week 20– Size: 10-12 inches long, 8 oz. – 1 pound– Senses of taste and smell formed– Hair and eyelashes developed– Movements can be detected by mother– Fetus sucks its thumb



• Week 24 (age of viability)– Size: 11-14 inches long, 1 pound to 1 pound 8 oz.– Eyes formed and open– Posture straightened and internal organs shift– Brain development occurs

• Week 28– Size: 14-17 inches long, 2 pounds, 8 oz. to 3 pounds– Body fat is accumulated– Body rhythms developing– Brain develops localized centers– Fetus can feel pain and touch; responds to sound and vibration



• Week 32– Size: 16 ½ - 18 inches long, 4-5 pounds– Rapid weight gain; body regulation becomes refined– Most bones formed– Fetus could survive without medical intervention

• Week 36-38– Size: 19 inches long, 6 pounds– Hearing is complete– Fetus shifts to “head-down”– Vernix caseosa falls away; lanugo dissolves– Antibodies are passed from the mother


Developmental Trends

• Three general trends characterize early developmental processes:– Cephalocaudal trend

• Development advances from the head to the feet

– Proximodistal trend• Development proceeds from the middle of the

body outward

– Gross-to-specific trend• Responses become more specific as development

advances


Developmental Trends• Three general trends characterize early

developmental processes:– Cephalocaudal trend

• Development advances from the head to the feet

– Proximodistal trend• Development proceeds from the middle of the

body outward

– Gross-to-specific trend• Responses become more specific as development

advances


Prenatal Environmental Influences

• Both genetic defects and environmental influences during the prenatal period or childbirth can result in congenital anomalies

• Maternal age is linked to increased incidence of congenital anomalies

– One in 25 mothers over the age of 45 will have a child with Down syndrome

– Age may be related to age of the ova, which may become damaged over time

– Hormone levels also shift as women age


Maternal Health and Nutrition

• Maternal malnutrition in pregnancy is linked to:– higher rates of spontaneous abortion

– premature birth

– stillbirth

– later difficulties in development

• Early quality prenatal care is associated with having healthy babies


Critical Periods in Prenatal Development

• A critical period is one during which the developing child is at the greatest risk for harm as a result of teratogens

• Sometimes exposure to a specific teratogen causes specific harm

• Or, exposure to certain teratogens may increase overall risk of damage


Critical Periods in Prenatal Development


Teratogens and Their Effects

• Viruses (HIV, rubella, the flu) may cross the placental barrier and affect the baby

• Using HAART therapy and Caesarian delivery, mother-to infant HIV transmission reduced to near zero

• Certain prescription drugs can cause damage



• Prenatal alcohol exposure: – May cause fetal alcohol affects or fetal alcohol

syndrome

– Also increases risk for learning disabilities, attention problems, and hyperactivity

– No amount of alcohol consumption during pregnancy is safe


Video Clip

Facts about fetal alcohol syndrome and faces of victims:http://www.youtube.com/watch?v=04IlEeh9vPs



• Marijuana exposure is linked to birth defects, structural defects, and cognitive deficiencies

• Cigarette smoking may lead to stillbirth, prematurity, spontaneous abortion, low birth weight and cognitive deficits

• Amphetamine drugs (e.g., cocaine) may damage the nervous system


Childbirth• Three stages:

– initial labor

– labor and delivery

– afterbirth

• Childbirth practices vary widely among cultures and generations

• Many women prefer natural childbirth today, though with medical assistance

• Birthing centers are becoming more common• Cesarean section used in 26% of U.S. births


Technological Innovations

• Allow physicians to detect problems early in pregnancy:

– Chorionic villus sampling (CVS)

– Ultrasound

– Amniocentesis

– Fetal monitors


Video Clip

Broadcast news story on 3D and 4D ultrasound technology:http://www.youtube.com/watch?v=ERTgbRnlAQw


Complications in Childbirth

• Breech presentation may require c-section

• Baby’s general health is evaluated on the 10-point Apgar Scale

• Prematurity is associated with:

– Low birth weight

– Difficulty adjusting after birth

– Behavioral problems in childhood


Video Clip

Describes the benefits of kangaroo care:http://www.youtube.com/watch?v=8hLo4_4ksAI


The Apgar Scoring System for Newborns


Video Clip

Description of the Apgar scale: http://www.youtube.com/watch?v=3C6F74Zs1BE


The Evolving Family• Birth is a psychological and social milestone for

the family

• The transition to parenting can be challenging– Pregnancy affects mothers emotionally and

psychologically, as well as physically

– Fathers may feel a greater sense of responsibility and concern about the future


Video Clip

Describes a nurse-family partnership program in Sacramento County, California that is in danger of being eliminated:http://www.youtube.com/watch?v=PwdiEtExyMg


The Newborn• The child experiences birth trauma

• Average full-term newborn weighs between 5 pounds, 8 ounces and 9 pounds, 8 ounces

• Typically between 19 and 22 inches long

• May have enlarged genitalia

• Upon birth, babies make major adjustments to their respiration, circulation, digestion, and temperature regulation


The Newborn

• Babies are born with two types of reflexes

– Survival

• Breathing, sucking, rooting, sneezing, gagging

– Primitive

• May have had survival value in evolutionary past, these reflexes disappear during first months of life


Video Clip

Description of the primary reflexes:http://www.youtube.com/watch?v=gyVLD0hl0XY


The Newborn

• Social and emotional processes of the infant will lead to development of attachment

• Attachment is reciprocal:

– Extends from infant to caregiver and visa versa

– For example, breast-feeding is good for mother and baby

• Infant-caregiver interactions shortly after birth establish the foundation of the attachment relationships that will continue through life


Summary

• Prenatal development is divided into three 3-month trimesters—germinal, embryonic, and fetal

• Three general trends characterize early development—cephalocaudal, proximodistal, and gross-to-specific

• Genetic defects and environmental influences (e.g., maternal age, malnutrition, and specific teratogens) can cause birth defects


Summary

• Childbirth is divided into three stages—initial labor, labor and delivery, and afterbirth

• Childbirth customs vary across cultures

• Cesarean sections are being increasingly performed, even when not medically necessary

• Premature is associated with low birth weight and early adjustment difficulties

• A baby’s general health can be evaluated on a scale called the Apgar Scoring System


Summary

• Birth marks a dramatic transition for newborns, who must make major adjustments to their respiration, circulation, digestion, and temperature regulations

• Babies are born with survival reflexes• Shortly after birth, babies and caregivers

engage in behaviors that will lead to attachment

• Attachment forms the foundation for later social and personality development

prenatal development and childbirth

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