4. Prenatal Devt and Birth Flashcards
prenatal development
the changes that transform the fertilized egg into a newborn human
how long is prenatal gestation?
38 weeks, +/- 5 weeks (on average)
what are the 3 stages of prenatal devt?
- zygote
- embryo
- fetus
zygote
a fertilized egg
how long is the zygote period?
about 2 weeks. ends when the zygote implants in the uterine wall
implantation
when the zygote burrows into the uterine wall
how long does implantation take? what happens?
about a week.
- the zygote burrows into the uterine wall and connects with the mother’s blood vessels.
- Hormonal changes are triggered that prevent menstruation.
- cells begin to differentiate.
germ disk
a small cluster of cells near the zygote’s centre that develops into a baby
placenta
the organ that exchanges nutrients and wastes between mother and baby
embryo
an embedded zygote (second stage)
what is the period of the embryo? what happens?
weeks 3-8
body structures and internal organs develop
ectoderm
the outer layer of the embryo that will become the hair, outer skin, and nervous system
mesoderm
the middle layer of the embryo that will become the muscles, bones, and circulatory system
endoderm
the inner layer of the embryo that will become the digestive systems and lungs
amniotic sac
the sac in which the baby develops (amnion)
amniotic fluid
the liquid that fills the amniotic sac and cushions the baby and maintain the temperature
umbilical cord
a cord-like structure containing blood vessels that joins the developing baby through the baby’s abdomen to the mother’s placenta
- the mother/baby blood vessels run close to each other but do not actually connect
- nutrients, oxygen, waste are exchanged
how does growth in the embryonic period happen?
cephalocaudal (top-down) and proximodistal (centre-out)
what is the period of the fetus? what happens?
weeks 9-38
baby grows and bodily systems start to work
cerebral cortex
grows during the fetal period.
it is the folded surface of the brain that regulates many human behaviours.
vernix
a thick, greasy coating on the skin that protects the baby during gestation
what is the age of viability? why?
22-28 weeks
the age at which the baby could survive outside the womb.
most of the systems are adequately developed and functioning.
What are the 3 general risk factors for prenatal devt?
nutrition
stress
age
What 3 areas does weight gain happen?
- 1/3 baby, placenta, amniotic fluid
- 1/3 fat stores
- 1/3 increase in blood, breasts, uterus
spina bifida
a disorder in which an embryo’s neural tube does not close properly during development. A result of inadequate folic acid in early preg.
What is the effect of stress on the baby?
- in animals, chronic stress results in smaller babies with more problems
- in humans, stress correlates with smaller, premature babies
- causes greater harm earlier in pregnancy
1. reduce oxygen to the fetus, increase heart rate & activity
2. weaken immune system -> illness
3. stress -> unhealthy lifestyle (e.g. smoking)
How does the mother’s age effect the pregnancy?
- teenage mothers are less likely to get prenatal care
- older age (40s) increases incidence of high-risk birth
teratogen (3 types)
an agent that disrupts normal prenatal development
- diseases
- drugs
- environmental hazards
what are two ways diseases can affect the baby?
- pass directly from the mother through the placenta
2. the virus is present in the birth canal and attacks at birth
fetal alcohol spectrum disorder (FASD)
a developmental disorder caused by maternal consumption of alcohol during preg
How do teratogens work (4 points)
- the impact depends on the genotype of the child
- the impact changes over the course of development (more and less vulnerable times)
- each one affects specific parts
- damage can appear later in life (not necessarily at birth)
ultrasound
a medical procedure that uses sound waves to generate an image of a developing baby
what can an ultrsound show?
- position
- sex (at 16-20 weeks)
- multiple pregnancies
- gross physical deformities
amniocentesis
a sample of amniotic fluid is taken (needle through the mother’s abdomen) to test for genetic disorders
- at 16 weeks
chorionic villus sampling (CVS)
a sample of placental cells is taken and tested for genetic disorders (tube through the vagina)
- at 8 weeks
advantages/disadvantages of Amniocentesis/CVS
A: test for 200 genetic disorders; error-free
D: higher risk of miscarriage
fetal medicine (3 examples)
a medical practice specially focused on treating fetal health problems in utero
- administering drugs/hormones via amniotic fluid or umbilical cord
- fetal surgery
- gene therapy
first stage of labour
uterine muscles contract, pushing amniotic fluid towards the cervix.
“transition stage”: contractions are most intense, sometimes occur without pause. cervix to about 10 cm.
second stage of labour
pushing urge
with the contractions, this pushes the baby down the birth canal and out
third stage of labour
placenta is expelled
3 strategies to counteract labour pain used in childbirth classes
- relaxation, deep breathing
- visual imagery
- a supportive coach
3 birth complications
- lack of oxygen
- prematurity
- low birth weight
anoxia
oxygen deprivation
- can occur during delivery of the umbilical cord is squeezed, or with placental abruption
- can lead to cognitive delay or death
placental abruption
when the placenta detaches from the uterine wall, severing connection to the mother’s blood supply
prematurity
when a baby is born less than 38 weeks after conception
- usually by age 2 or 3 they catch up developmentally
- greatest risk is to underdeveloped cerebellum - effecting cognition, behaviour, attention, socialization
small-for-date infants
babies who are substantially smaller at birth than expected based on length of time since conception
- often because of smoking/drinking/inadequate nutrition
- developmental issues; can be moderated by a stable, supportive environment
infant mortality
the number of infants out of 1000 births who die before their first birthday (Canada = 5)
Apgar score
a numerical scale used to rate a newborn baby’s vital signs (0-1-2). Score of 7+ indicates good health.
- appearance (skin tone)
- pulse (heartbeat)
- grimace response (presence of reflexes such as coughing)
- activity (muscle tone)
- respiration (breathing)
Neonatal Behavioural Assessment Scale (NBAS)
evaluates a broad range of newborn abilities and behaviours that the baby needs to adjust to life outside: reflexes, hearing, vision, alertness, irritability, consolability
4 newborn states
- alert inactivity
- waking activity
- crying
- sleeping
3 types of crying
- basic cry - starts soft, gets more intense (hunger, tired)
- mad cry - more intense version
- pain cry - a sudden long burst, followed by a long pause and gasping
REM sleep
rapid-eye-movement; a period of sleep involving small physical movements or twitches
- may stimulate the brain to foster nervous system growth
- increased production of proteins in the brain
- stimulation of learning and memory
Non-REM sleep
a period during sleep that is motorically quiet and involves steady breathing, heart rate, and brain activity
why is sleep important in infancy?
- facilitates neural maturation - good for learning
- consolidates memory for waking events
- helps process sensory stimuli and relationships
- better immune function
sudden infant death syndrome (SIDS)
a healthy baby dies suddenly and unexpectedly, for no apparent reason.
- more vulnerable is premature or small-for-date
post-partum depression
feelings of low self-worth, disturbed sleep, poor appetite, and apathy in the months after delivering a baby.
- biological and environmental influences
- affects babies if it lasts too long - likely to have depression and behavioural problems
First cell division ? hours after conception
36
blastocyst
the fertilized egg 4 days after conception, which consists of about 100 cells and resembles a hollow ball
general Risk Factors in Prenatal Development
- nutrition
- stress
- mother’s age
teratogen
an agent that causes abnormal prenatal
development
neonate
the newborn baby up to 4 weeks old
Average “dimensions” of the neonate
Length: 50 cm (20 inches)
Weight: 3.4 kg (7.5 lbs)
Moro reflex
Stimulation: Dip downward suddenly or loud sound
Response: Arch back, extend arms and legs outward,
bring arms together swiftly
Relic of primate adaptive reaction to grab when falling?
Sucking reflex
Stimulation: Object or substance in mouth
Response: Sucking
Method of taking in nutrition
grasping reflex
Stimulation: Object placed in palm
Response: Baby holds object tightly
swimming reflex
Stimulation: Baby is immersed in water
Response: Holds breath, swims with arms and legs
Precursor to voluntary swimming movements that
develop later
Babinski reflex
Stimulation- Stroke sole of foot
Response- Foot twists in, toes fan out
Purpose unknown
Rooting reflex
Stimulation- Touch on cheek or mouth
Response- Turn toward touch
Helps baby find food.
stepping reflex
Stimulation- Hold baby under arms with feet touching floor Response- Baby makes stepping motions Precursor to voluntary stepping motions that develop later
low birth weight
less than 2500g (5.5 lbs)
very low birth weight
less than 1500g (3.3 lbs)
extremely low birth weight
less than 1000g (2.2 lbs)
Risk factors for preterm birth and low birth
weight:
- poor maternal nutrition
- poor maternal health (illness/disease)
- lack of prenatal care
- maternal smoking, drug or alcohol use
- multiple births
- young (<17 years) or old (>40 years) maternal age
Why are preterm babies at risk?
- undeveloped immune system
- immature central nervous system
- undeveloped lungs
- lack of body fat unable to maintain body heat
Children born preterm are more likely to have
problems or difficulties in the following areas:
- IQ & cognitive functions (e.g., memory)
- attention
- gross and fine motor skills (e.g., Cerebral Palsy)
- hand-eye coordination
- academic performance
- language
