Chapter 4 & 5 Notes 2007
Chapters 4 & 5
Wednesday,
January 31, 2007
Prenatal Development & Birth
From Zygote to Newborn
Germinal Stage – The first 14 days after conception
Embryo – From the 3rd week to the 8th week
Fetus – From the 9th week until birth
Length of pregnancy – 38 weeks
Divided into trimesters (approx. 3 months)
Due date – estimate based on length of pregnancy
Prenatal Development & Birth
Germinal – the first 14 days
Germinal period- The first 2 weeks of development after conception; characterized by rapid cell division & the beginning of cell differentiation
At about a week after conception, outer cells form an shell – the placenta – which then attempts to implant itself into the uterine wall
Approx. 60 -70 % of fertilized eggs fail to implant. Failure to implant – no pregnancy
Prenatal Development & Birth
Embryonic Period – Approximately the 3rd thru 8th week after conception. The period during which the basic forms of all body structures develops.
The first human structure to develop – neural tube – (develops into the brain, spinal cord and the central nervous system)
At 4 weeks – head begins to take shape, facial features form, and a heart beat can be detected
At 8 weeks – the embryo weighs about 1 gram & is about 1 inch long.
Prenatal Development & Birth
Fetal Period – From the 9th week until birth. The period in which the organs of the developing person grow in size and mature in function.
Referred to as a fetus.
During the third month, sex organs begin to take shape.
By the end of the 3rd month, the fetus has all body parts, weighs approximately 3 ounces and is about 3 inches long.
Fetal Development – 4 Months
Prenatal Development & Birth
The middle months (2nd trimester)
Heartbeat becomes stronger, digestive and excretory systems develop.
Brain increases in size six fold. Countless neurons develop.
As brain function develops, the age of viability can be as early as 22 weeks.
Age of viability – The age at which a fetus can survive outside the mother’s uterus with additional medical support.
At 28 weeks – the fetus weighs about 3 pounds.
Prenatal Development & Birth
The Third Trimester – Develop from viable to full term.
Lungs & circulatory system continue to develop & become more mature & refined. If delivered at term, usually no special breathing nor feeding apparati are needed.
The fetus gains about 4 lbs. during the last trimester
Prenatal Development & Birth
Risk Factors During Pregnancy
Teratogens – Are substances (drugs or pollutants) and conditions (stress or malnutrition) that increase the risk of prenatal abnormalities.
Behavioral teratogens – Teratogens that can harm the prenatal brain and increasing the likelihood of developing ADD, Learning Disabilities, and other behavioral disorders
Incidence – 3% in general population
Prenatal Development & Birth
Risk Analysis – Weighing the factors that determine the likelihood that a particular teratogen will cause harm.
Exposure increases the risk
Not all exposed will have damage
Critical Period – The time when a particular organ or other body part is most susceptible to teratogen damage
Risk = exposure + time
Prenatal Development & Birth
Some teratogens have a threshold effect. This means that a teratogen is harmless in a small amount, but it does become harmful if it reaches a certain level. (vitamin A)
Interaction – mixing of teratogens. (smoking & drinking while pregnant)
Risk = exposure + time + amount
Prenatal Development & Birth
Risk = exposure + time + amount + genetic make-up
Note folic acid deficiency – governmental law and reduction in neural tube defects
Book – HIV and Fetal Alcohol Syndrome
Prenatal Development & Birth
Low Birth weight – Defined as less than 5 and ½ lbs. at birth.
The incidence (rate) of this is 7.6% of all U S newborns.
Low birth weight is the 2nd most frequent cause of neonatal death.
Preterm Birth – Birth that occurs 3 weeks or more before full term pregnancy
Small for Gestational Age – A birth weight that is significantly lower then expected, given the time since conception.
Prenatal Development & Birth
Maternal behavior is a more common cause of SGA than illness. Cigarettes is the most prevalent cause of this.
Maternal malnutrition is also a contributor to SGA.
Prenatal Development & Birth
Birth Process
Fetus inverts – head faces down
Hormones are released which start uterine muscle contractions
The amniotic fluid is discharged from the amniotic sac
The cervix opens to approximately 10 centimeters (the size of a fist)
The fetus head crowns and goes out the birth canal into the world.
Prenatal Development & Birth
Congratulations – We now have a newborn……
Medical staff or midwifes do the following:
Remove any mucus from mouth and nose
Umbilical cord is tied off and ready to be cut
Neonate is weighed and wrapped to keep it warm
APGAR scale is done at 1 and 5 minutes after birth
Prenatal Development & Birth
APGAR – Neonates are measured in 5 areas, on a scale from 0, 1 or 2
Heart Rate Muscle tone
Reflexes Coloring of the flesh
Respiratory effort
7 or better – normal
4 or less - distress
Prenatal Development & Birth
Cesarean Section – Surgical birth where the abdomen and uterus are cut to allow the fetus to come out
Lots of debate over c-sections
One study – 17% for those with insurance
14 % Medicaid - 10% for those with no insurance
High rate of c-sections in Latin America
Prenatal Development & Birth
Birth Complications
Cerebral Palsy – Disorder that results from damage to the brain’s motor centers. Thought was a by-product of birth procedures
CP usually results from genetic vulnerability and may be worsened by teratogens and a temporary lack of oxygen (anoxia) to the brain.
Prenatal Development & Birth
Taking your newborn home
Bonding – A strong, loving connection that forms when parents hold, examine, and feed their newborn.
Postpartum Depression – A mother’s feelings of sadness, inadequacy, and hopelessness in the days & weeks after giving birth. (Partly hormonal, partly cultural, and partly spousal)
The 1st 2 Years – Biosocial Development
Tremendous physical growth – go from about 20 inches at birth to half of their adult height by the time they are 2.
At 2, they weigh approximately 4 times their birth weight.
If this rate of growth continued, would be the size of an elephant by 14.
The 1st 2 Years – Biosocial Development
New babies spend about 17 hours a day sleeping.
As we sleep, the brain matures. Sleep helps in adjustment and daily functioning.
REM Sleep – Rapid Eye Movement, in which dream sleep takes place (eyes flicker while shut, rapid brain wave activity)
Schedule – What schedule is the infant on?
The 1st 2 Years – Biosocial Development
Norms and percentiles
Norm – a standard or average measurement, calculated from many individuals within a specific population
Percentile – A ranking scale from 1 to 99. Where 50 is the median, or where exactly half of the people a above the scale and exactly half are below the scale.
The 1st 2 Years – Biosocial Development
Early Brain Development
At birth, the brain is 25% of it’s adult weight.
Brain is composed of Neurons – a nerve cell
Cortex – The "thinking" part of the brain, where approximately 70% of the brains neurons are located
Axon – Nerve fiber, covered in myelin. The axon sends messages to other neurons.
Dendrite – Fiber that extends from a neuron and receives electrical impulses from other neurons
Synapse – Tiny gap between the axon of one neuron and the dendrite of another
Neurotransmitters – Chemicals that carry the nerve signal from 1 dendrite to the other.
The 1st 2 Years – Biosocial Development
At birth, more neurons are in the brain than we will ever need.
However, far fewer dendrites and synapses than we will eventually have.
Transient exuberance – The great increase in the number of dendrites that occur in an infant’s brain during the infants first two years.
The 1st 2 Years – Biosocial Development
As the infant experiences the environment, associations are formed and begin to develop into behavior patterns. (Book mentions stress)
2 experience-related aspects of brain development have been identified by William Greenough.
Experience Expectant – Brain functions that require basic common experiences to develop in all infants
Experience Dependent – Brain functions that depend on particular & variable experiences – may not develop in all infants (particular language)
The 1st 2 Years – Biosocial Development
Key areas for development – holding, talking, and showing affection are critical towards optimal development.
Infant brain development is dependent on sensory experiences & movement of the infant.
Piaget – Sensorimotor Stage
The 1st 2 Years – Biosocial Development
Infants have all 5 senses functioning
Sensation – The response of a sensory system (eyes, ears, skin, nose, tongue) when it detects a stimulus
Perception – The mental processing of sensory information, when the brain interprets a sensation.
Perception processing occurs in the cortex, - the "thinking" part of the brain.
The 1st 2 Years – Biosocial Development
Cognition – Thought about what one has perceived.
Process – Sensation – Perception – Cognition
As the infant grows older, development relies more on cognition
The 1st 2 Years – Biosocial Development
Listening – quite acute at birth. May even trigger certain reflexes.
As development progresses, hearing + cognition merge to help form language.
Vision – Least developed sense in the newborn.
Binocular vision – The ability to focus the two eyes in a coordinated manner in order to see one image.
The 1st 2 Years – Biosocial Development
Taste, Smell, & Touch
These senses are functioning at birth.
There are some early preferences for certain stimuli (sweets, soft and warm)
(Rocking to soothe a crying newborn)
Senses are organized for 2 goals:
Social Interaction
Comfort
The 1st 2 Years – Biosocial Development
Motor Skill Development – Go from being unable to change position to walking in about 2 years.
Reflexes – A responsive movement that seems automatic, because it almost always occurs in reaction to a particular stimulus
Reflexes to maintain oxygen – breathing reflex
Reflexes to maintain body temperature – cry, shiver
Reflexes that manage feeding – sucking and rooting reflex
The 1st 2 Years – Biosocial Development
Gross Motor Skills – Physical abilities involving large muscle movements, such as walking & jumping.
Emerge directly from reflexes.
Progression of behaviors that eventually are combined to form a target behavior.
Rolling over – 4.7 months – 90%
Sitting by themselves – 7.8 months – 90%
Cruising – 12.7 months – 90%
Walking – 14.3 months – 90%
The 1st 2 Years – Biosocial Development
Fine Motor Skills – Physical abilities involving small body movements, particularly the hands & fingers
Wave arms & miss an object in front of them at 2 months
Reach & grab an object at 4 months
Transfer an object from one hand to another at 6 months (Developmental milestone)
At 1 year, point and reach
The 1st 2 Years – Biosocial Development
Public Health Issues
Immunizations – A process that stimulates the body’s immune system to defend against attack by a particular contagious disease
Schools, day cares, require immunizations for admission.
Can "opt out" for religious reasons,
The 1st 2 Years – Biosocial Development
Other health related issues
Sudden Infant Death Syndrome (SIDS)
A situation in which a seemingly healthy infant, at least 2 months of age, dies unexpectedly in his or her sleep.
Deaths due to SIDS are dramatically decreasing
Put infants to sleep on their backs and parents have decreased smoking around their infants.
The 1st 2 Years – Biosocial Development
Breast Feeding vs. Bottle feeding
Mothers milk contains nutrients that are better suited for the newborn to process and use in development
Bottle feeding is inexpensive & convenient, especially if the mother has to go back to work in 6 weeks after giving birth.
The 1st 2 Years – Biosocial Development
Malnutrition
The most serious is protein-calorie malnutrition
A condition in which a person does not consume sufficient food of any kind.
Ascertained in infants by using weight norm tables and percentiles
Effects of malnutrition
Brains do not develop normally
Immune system is weak
Body deformity or in severe cases, death
