Chapter 2 Review: Prenatal Development, Birth & the Newborn

what are gametes?

reproductive cells—egg and sperm—that contain only half the genetic material of all the other cells in the body; they have 23 chromosomes each due to meiosis

what is meiosis?

a form of cell division that produces gametes

what is conception?

the union of an egg and a sperm

what are the 3 key stages of prenatal development?

1. germinal / zygote

2. embryonic

3. fetal

when is the germinal / zygote period?

conception to 2 weeks

when is the embryonic period?

3rd to 8th week

what is an embryo?

the developing organism from 3rd to 8th week of prenatal development

what is a fetus?

the developing organism from the 9th week to birth

when is the fetal period?

9th week to birth

What are the 4 major developmental processes of prenatal development (from zygote to embryo to fetus)?

1. mitosis

2. cell migration

3. cell differentiation

4. apoptosis

what is mitosis?

cell division that results in two identical cells

what is cell migration?

the movement of newly formed cells away from their point of origin

what is cell differentiation?

process of cells transforming from embryonic stem cells to specialized cells

what are embryonic stem cells?

embryonic cells that can develop into any type of body cell

what is apoptosis?

genetically programmed cell death

what is an e.g. of apoptosis?

the development of the hand as it requires the death of the cells in between the ridges of the hand plate in order for the fingers to separate

what is the period of zygote (weeks 1-2)?

• begins when egg is fertilized in the fallopian tube

• period of rapid cell division

• after about 4 days, the zygote is called a blastocyst

• ends 2 weeks later when the zygote is implanted in the wall of the uterus

• placenta is formed between mother and developing organism to provide nutrients and remove waste

what are identical (monozygotic) twins?

twins that result from the splitting in half of the zygote, resulting in each of the two resulting zygotes having exactly the same set of genes

what are fraternal (dizygotic) twins?

twins that result when two eggs happen to be released into the fallopian tube at the same time and are fertilized by two different sperm; have only half their genes in common

what is ectopic pregnancy?

pregnancy in which the fertilized egg implants and grows in an organ outside of the uterus (most often in a fallopian tube), preventing normal growth of the fetus and putting the expectant parent at risk of life-threatening injury

what is the leading cause of maternal deaths in the 1st trimester?

ectopic pregnancy

what is the placenta?

a support organ for the fetus; it keeps the circulatory systems of the fetus and pregnant parent separate, but a semipermeable membrane permits the exchange of some materials between them (oxygen and nutrients from pregnant parent to fetus, and carbon dioxide and waste products from fetus to pregnant parent)

what is cephalocaudal development?

the pattern of growth in which areas near the head develop earlier than areas farther from the head

what is the period of the embryo (weeks 3-8)?

• body structures and internal organs are formed during this period

• embryo rests in the amniotic sac filled with amniotic fluid

• umbilical cord joins embryo to placenta

what are the three layers of the inner cell mass during the embryo period?

1. ectoderm

2. mesoderm

3. endoterm

what does the ectoderm layer develop?

hair, outer layer of skin, nervous system

what does the mesoderm layer develop?

muscles, bones, circulatory system

what does the endoderm layer develop?

digestive system & the lungs

what is the amniotic sac?

a transparent, fluid-filled membrane that surrounds and protects the fetus

what is spina bifida?

• a birth disorder in which the spine doesn’t fully develop

• neural tube doesn’t close completely, and some of the bones of the spine do not close in the back

• the openings can be anywhere along the spine and damage the spinal cord and nerves

what are risk factors for spina bifida?

• genetics, environment, nutrition

• importance of folic acid

what is the period of the fetus (weeks 9 to 38-40)?

• from 9 weeks after conception to birth

• the finishing touches are put on the body systems

• all regions of the brain grow, particularly the cerebral cortex

• genital organs fully develop in the 3rd month

• the skin is covered with a thick, greasy substance called vernix

when do fetuses start to show variations in heart rate in response to physiological stress?

6 months

when will most of the movements that will be present at birth appear?

by 12 weeks

what forms of prenatal movement occur at 12 weeks?

• swallowing amniotic fluid

• movement of the chest wall

why do fetuses swallow amniotic fluid?

promotes the normal development of the palate and aids in the maturation of the digestive system

why do fetuses pull in/expel small amounts of amniotic fluid?

helps the respiratory system become functional

what kinds of prenatal sensation occur?

• fetus experiences tactile stimulation, taste and smell

• it responds to sounds around the 6th month of gestation

• prenatal visual experience is negligable

what is habituation?

a simple form of learning that involves a decrease in response to repeated or continued stimulation

what was the cat in the hat study (decasper & spence)?

• 7 ½ month pregnant women read the target story aloud 2x a day

• newborns tested using nonnutritive sucking procedure

• some heard mother read stories; others heard unfamiliar woman read stories

• preference control: tested group of infants whose mothers had not read the stories during pregnancy

• proved that human fetuses can hear and learn and remember sounds from inside the womb

what are the 2 main hazards to prenatal development?

teratogens and parental factors

what is a teratogen?

an external agent that can cause damage or death during prenatal development

what is the sensitive period?

the period during which a developing organism is most sensitive to the effects of external factors

what was thalidomide?

• was prescribed to treat morning sickness (amongst other things) and was considered to be so safe that it was sold over the counter

• serious defects occurred only if the drug was taken between the 4th and 6th week after conception—the time when the fetus’s limbs were emerging and developing

what is fetal programming?

the belated emergence of effects of prenatal experience that help determine physiology in adulthood

what is an e.g. of fetal programming?

• the dutch hunger winter

• at this point in wwii, the german occupying force in the netherlands limited rations to as little as 400 to 800 calories per day

• while babies born during this time were of normal birth weights, they grew up to have high rates of obesity

• the fetuses’ metabolisms were apparently set prenatally, while they were experiencing undernutrition, and were not reset when nutrition reached normal levels

what is the sleeper effect?

the impact of a given agent may not be apparent for many years

what is an e.g. of the sleeper effect?

• between the 1940s and 1960s, the hormone diethylstilbestrol (DES) was commonly used to prevent miscarriage and had no apparent ill effects on babies born to parents who had taken it while pregnant

• however, in adolescence and adulthood, these offspring turned out to have elevated rates of cervical and testicular cancers

what are the impacts of nicotine on prenatal development?

• delayed growth and low birth weight

• constricts blood vessels in the placenta

• linked to SIDS (sudden infant death syndrome) & ADHD

• harmful when combined with cannabis

what are the impacts of alcohol on prenatal development?

• fetuses do not have fully developed livers so they cannot break down & it stays in their system for a longer time

• kills cells in different parts of the fetus with abnormal physical development

• interferes with the development of central nervous system

• constricts blood vessels, impacts nutrients supply from placenta

• risk of miscarriage, premature birth, low birthweight

• affects central nervous system the most

what is fetal alcohol spectrum disorder (FASD)?

the harmful effects of alcohol consumption on a developing fetus, including characteristic facial features, intellectual developmental disorder, attentional challenges, and hyperactivity

what is the most common nonheritable causes of intellectual disability?

FASD

what are some symptoms of FASD?

• acting impulsively

• difficulties handling money, keeping up with classroom learning

• not understanding consequences

• being unfocused and/or easily distracted

• physical health issues (heart, vision, hearing)

what is fetal alcohol syndrome (FAS)?

• the most severe condition on the spectrum

• abnormal facial features

• low weight

• small head size

• abnormalities of their brain development that could cause seizures

• language or learning problems, and/or intellectual disability

• significant impulsivity or behavior problems

• high risk of developing ADHD, intellectual disability, anxiety disorder, impulsive behaviours, language and learning problems

what are the prevalence rates of FASD?

• about 8% in north america, 4% in canada

• rates in indigenous communities vary dramatically (0.7% to 27%)

what are social determinants of health?

non-medical/social and economic factors that determine one’s health (e.g., income, education, housing, access to food and healthcare, experiences of discrimination, intergenerational trauma, stress).

what are environmental hazards for prenatal development?

• lead, mercury

• air pollution

• methylmercury poisoning (in grassy narrows community and white dog first nations)

• nanoplastic in placenta

what are parental factors to prenatal development?

• age

• nutrition

• disease

• emotional state

how does age impact prenatal development?

• infants are 3-4 times more likely to die if mother is younger than 15

• for women aged 15-19, pregnancy and birth-related conditions are the leading cause of death

• children born to older parents are at heightened risk for developmental disorders such as autism, down syndrome, schizophrenia, bipolar disorder

how does nutrition impact prenatal development?

• fetus depends on the pregnant parent for all its nutritional requirements

• bcause malnutrition is more common in low-income families, it often coincides with the host of other risk factors associated with poverty, making it difficult to isolate its effects on prenatal development

how does disease impact prenatal development?

• some like rubella can have wide-ranging developmental effects, including deafness, blindness, and intellectual developmental disorders

• others, like STIs, can damage the fetus’s central nervous system and cause a variety of other serious defects, including hearing loss

does COVID-19 have any impacts on pregnancy?

• was associated with preeclampsia, preterm birth, stillbirth, gestational diabetes, and low birth weight.

• so far, no concerns regarding vaccination during pregnancy

• so far, no neurodevelopmental abnormalities associated with exposure during pregnancy

how does emotional state impact prenatal development?

prolonged stress decreases oxygen to fetus, weakens mother’s immune system, and leads to unhealthy behaviours such as smoking or drinking alcohol

what are symptoms of prolonged stress on baby?

• lower birth weight

• premature birth

• newborn irritability

• feeding and sleeping problems during infancy

• behaviour issues that begin at age 4

when does labour happen?

• 34-40ish weeks

• we still don’t know what triggers labour

• placenta as a biological clock

• fetal lungs secrete a protein when ready

why are we born at 9ish months?

• human babies’ heads are underdeveloped compared to other primates

• would take 21 months to get there

• trade-off between bigger heads and smaller pelvises that we need for bipedal walking

• could also be due to our metabolism, by 6 months pregnant women expend x2 energy

what are the stages of labour?

1. stage 1: starts when the muscles of the uterus contract and ends when the cervix is fully enlarged (about 10 cm)

2. stage 2: baby is pushed through birth canal

3. stage 3: placenta is expelled

what is the latent period of cervix?

0 to 6 cm

what is the active period of cervix?

6 to 10 cm

what is hypoxia?

can occur during labour and delivery if the umbilical cord is pinched or squeezed shut, cutting off the flow of the blood to baby

what is a caesarean section (c-section)?

an incision is made in the abdomen to remove the baby from the uterus

what are the reasons for c-section?

• breech presentation

• shoulder presentation

• syphilis, herpes simplex, AIDS

• previous c-section

• multiple births

• fetal distress (e.g. cord entangled)

what is the apgar test?

the test that assesses five vital signs in the newborn

what does apgar stand for?

Appearance (skin tone)

Pulse (heart rate)

Grimace (reflexes)

Activity (muscle tone)

Respiration (breathing)

what is the apgar scoring?

• 0-3: severe neonatal distress (bad)

• 4-6: moderate neonatal distress

• 6-10: normal newborn (good)

how much do newborns sleep?

• 16-18 hours daily

• cycles of wakefulness and sleep every 4 hours (1 hour awake, 3 hours alseep)

what is REM sleep?

• an active sleep state characterized by quick, jerky eye movements under closed lids and associated with dreaming in adults

• constitutes fully 50% of a newborn’s total sleep time

why do babies spend so much time in REM sleep?

• it helps develop the infant’s visual system

• the natural jerking movements that occur exclusively during this sleep may give infants opportunities to build sensorimotor maps

what is sudden unexpected infant death (SUID)?

• occurs when a healthy baby dies for no apparent reason

• includes all unexpected deaths - includes those with a clear cause (like suffocation) and those without (SIDS)

what is the leading cause of infant deaths under the age of 1?

SIDS (sudden infant death syndrome)

what is a premature/preterm birth?

a baby born before 37 weeks of gestation (ranges 28 to 36)

what is a low birth weight?

a birth weight of less than 5.5 pounds (2500 grams)

what is small for gestational age?

babies who weigh substantially less than is normal for whatever their gestational age

what is kangaroo care?

a variant of the skin-to-skin care in which caregivers act as incubators to help maintain infants’ skin temperature—decreases mortality and increases growth, breast-feeding, and attachment

what is postpartum depression (PPD)?

• is the most common complication of childbirth

• includes suicide risk which accounts for up to 20% of all pp death

what are the risks/impacts of PPD?

• impairs infant safety and health child development and leads to infantile colic and poor maternal-infant bond

• may affect IQ, language development and behaviour

• reduced sleep, increased nocturnal awakenings, altered sleep schedule, worse subjective sleep quality