Infancy Prenatal Development Birth NICU PDF

Summary

This document discusses prenatal development, covering various stages from conception to birth. It explains concepts like preformationism and epigenesis, and details the germinal, embryonic, and fetal periods, including development of major organs, sex differentiation, and the process leading to the formation of twins.

Full Transcript

Prenatal Development: Introduction Infancy Module 4 1 Preformationism Theory of development in which prenatal life starts with a fully- formed individual that gets bigger Debates about...

Prenatal Development: Introduction Infancy Module 4 1 Preformationism Theory of development in which prenatal life starts with a fully- formed individual that gets bigger Debates about whether tiny person was in sperm or egg The Homunculus Believed for most of human history Still exists in some form in some religions ULTIMATE NATIVIST ACCOUNT 2 Preformationism is patently false. Aristotle coined the term epigenesis = the emergence of new structures and functions during development Fetuses of different looked at chicken eggs species look more like each other than like what they become 3 Canalization Refers to developmental reduction in plasticity Initially cells can become anything (stem cells); as development progresses, it’s harder to change paths Studies with frogs: you can change a cell’s path by simply Waddington’s moving it - development Epigenetic in uenced by neighbouring cells Landscape Or, wiping out a brain area early on... 4 fl Preformationism patently false, but... Wide cultural variation in views on “when life begins” Conception? (when sperm enters egg) When fetus can feel pain? Birth? The Beng of West Africa think even later - birth is reincarnation of an ancestor Life begins when newborns choose not to return to wrugbe (afterlife) You know they've chosen to stay when their umbilical stump drops off (couple weeks post birth) 5 A note on length of pregnancies You will typically hear of women being “full term” at 40 weeks of pregnancy This is ~40 weeks since last period — the time from conception to birth is ~38 weeks Conception happens sometime around 2 weeks after last period, but hard to know when (unless IVF) This class will use time post conception (=38 weeks), as there is no pregnancy before then 6 Sex cells Gametes = eggs and sperm Eggs are much bigger (largest cell!) and all formed prenatally; sperm much smaller and formed throughout lifespan haploid = only half the genetic material found in other diploid cells Contain 23 chromosomes v. 23 pairs of chromosomes 7 Fertilization & Conception While millions of sperm are ejaculated, only ~200 reach the egg (most get lost, tangled up, or have other genetic defects - survival of the ttest!) Takes about 6 hours to go 6-7 inches When one penetrates, zona reaction occurs, blocks other sperm from entering sperm tail falls off and rest goes into egg zygote = fertilized egg with (hopefully) 23 chromosomes from mom and 23 from dad 8 fi Principles of Prenatal Development Cephalocaudal = head rst Basic rst, then more specialized => arm buds, then hand paddle, then ngers Important rst => brain and heart Mooney, 2021; Medscape 9 fi fi fi fi Processes of Prenatal Development Four major developmental processes transform a zygote into an embryo and then into a fetus: 1. Cell division = mitosis results in the proliferation of cells 2. Cell migration the movement of cells from their point of origin to somewhere else in the embryo 3. Cell differentiation transforms the embryo’s unspecialized stem cells into roughly 350 different types of cells 4. The selective death of certain cells, or apoptosis, also enables prenatal development hand development 10 Prenatal Development: Germinal & Embryonic Periods Begins with conception and lasts until the zygote becomes implanted in the uterine wall. Rapid cell division takes place. Germinal (conception - 2 weeks) Following implantation, major development occurs in all the organs and systems of the body. Embryonic (3rd - 8th week) Fetal (9th week - birth) 11 Germinal Period: The Morula & Blastocyst Inner Cell Mass Conception becomes baby, rest becomes placenta and amniotic sac 12 Twins! Determined during Germinal Period Monozygotic = Identical; inner cell mass splits Siblings share 100% genetic material (well, not exactly) Dizygotic = Fraternal; 2 eggs released and fertilized by diff sperm Siblings share 50% genetic material i.e. no more related than non- twin sibs 13 Twins! Identical/MZ - usually share same placenta (with own amniotic sacs) not always - if split happens in rst 2 days environmental difference! if split happens late, may share same sac - risk of umbilical cord entanglement very late - conjoined IDENTICAL TWINNING IS NOT HEREDITARY, while fraternal/DZ twinning is (tendency for hyper-ovulation can be passed down) Fun fact: The children of identical twins (cousins) are genetically equivalent to half-sibs (Share 25% genes v. 12.5%). If two sets of MZ twins marry, their kids are genetic equivalent of full sibs! (50%) 14 fi The Embryonic Period Blastocyst implants into uterine wall - now an embryo! Placenta and amniotic sac form, chemicals released to preserve pregnancy Most sensitive period of development Rapid cell division Major organs forming Most miscarriages happen here 15 Amniotic Sac/Placenta Amniotic sac lled with amniotic uid - protects baby, lets it move unhampered by gravity Placenta is a network of blood vessels that allows for exchanging uids between fetus and mom connected to embryo by the umbilical cord semipermeable - let good stuff in and bad stuff out also lets some bad stuff in! also produces hormones (estrogen, progesterone) 16 fl fl fi The Embryo In weeks 2-3, inner cell mass folds into 3 layers: top = nervous system, nails, teeth, inner ear, lens of eyes, outer surface of skin middle = muscles, bones, circulatory system, inner layers of skin, other intestinal organs bottom = digestion, lungs, urinary tract, glands Top layer folds in on itself and becomes the neural tube Becomes the brain and the spinal cord Spina bi da results from closure errors here (take folic acid) 17 fi 4 Weeks primitive heart Neural Tube (nearly closed) begins to pump blood 18 Facial Development 5.5-8 weeks Cleft palate happens here 19 6-8 weeks 3/4 inch long heart has 4 chambers ngers and toes visible major organs forming movement begins (bending spine) 20 fi Prenatal Development: Fetal Period Germinal (conception - 2 weeks) Embryonic (3rd - 8th week) Continued development of physical Fetal structures and rapid growth of the (9th week - birth) body. Increasing levels of behaviour, sensory experience, and learning. 21 9 weeks: A fetus! Extremely rapid brain growth All internal organs present Rudimentary ears and eyes Fingers and toes present 22 11 weeks 2.5 inches long fetal ‘breathing’ begins heart has 4 chambers brain has major divisions sleep and awake states begin period of lower body growth Sexual differentiation begins most spontaneous abortions occur before this point 23 Sexual Differentiation All about hormones! Androgens, including testosterone, are produced by all fetuses, but the genetically male fetus (determined entirely by the sperm provided by genetic father) produces a lot more Causes testes to develop; these eventually produce testosterone themselves Testosterone in a genetic female (xx) can cause male anatomy and brain differentiation = congenital adrenal hyperplasia Lack of sensitivity to testosterone in a genetic male (xy) causes no male organs; individuals often raised as female = androgen insensitivity syndrome Sex chromosome abnormalities in 1/500 births 24 Sex =/= Gender Sex is the genotype Gender is the phenotype = what is expressed Gender identity present from age 2 or 3, both cisgender and transgender children identify gender reliably by age 5 (You should really call them “sex reveal parties”) 25 Sex-Linked Inheritance Males more susceptible to express recessive X- linked traits Only one chance to get a “clean” copy; whatever males have will be expressed Hemophilia, Fragile-X syndrome Y-linked traits will only affect males; pass from father to son Webbed toes 26 18 weeks Can now blink, grasp, move its mouth, and suck its thumb Sex detectable Mother may be able to feel the fetus moving All organs formed, period of simple growth begins Facial expressions Lungs are formed, but not developed enough to survive outside the womb Covered in hair and greasy substance Fetus may be able to feel pain 16 weeks 27 22 Weeks About 7.5 inches long, weighs about 1 pound Has ngerprints! Facial movements - can raise eyebrows Time of extremely rapid brain growth Might be able to survive outside the womb 8-9 inches from head to rump, weighs 1-1.5 pounds Lungs are capable of breathing air, may need assistance if outside womb Can smile, frown, cry, and squint Apoptosis begins on large scale (24 wks) 20 Weeks 28 fi 28 weeks 10.5 inches from head to rump, weighs 2.5 pounds Lungs are capable of breathing air Hears and reacts to a variety of sounds Almost always survive outside womb Brainwaves like newborns’ Between 28 weeks and term, fetus mainly grows (dramatically) in size 29 38 weeks (from conception) = Full term (40 weeks from last period) 30 Fetal Activities Movement: Fetuses move from 5-6 weeks! 7-week-old fetuses hiccup Activity level individual differences, and there’s continuity in this after birth More active fetuses = more active, less inhibited children Seem to “practice” for life outside the womb: Bringing hand to mouth Swallowing amniotic uid promotes development of the palate and aids in the maturation of the digestive system Movement of the chest wall and pulling in and expelling small amounts of amniotic uid help the respiratory system become functional called “fetal breathing” - only 50% of time Cells in visual pathway engage in spontaneous activity 31 fl fl Fetal Behavioural Cycles Young fetuses move a LOT - pretty much all the time jerky, uncontrolled After 10 weeks, rest/activity cycles every few minutes In second half of pregnancy, move only 10-30% - thought to be related to cortical inhibition Most active in early morning and late evening By end of pregnancy, sleep about 75% of the time (like newborns); with distinct sleep states 32 Fetal Senses Fetus feels, tastes, smells, and hears Feels own movements Tastes and smells amniotic uid (sweet=good) Hears mom’s bodily sounds (it’s loud in there!); her voice; startles to loud sounds Hair and neural cells tune to different sounds from 25 weeks Important environment isn’t too loud Seeing minimal (eye mainly develops prenatally = they can see, but it’s dark in there!) Cells in fetal visual pathway engage in spontaneous activity, “practicing” for after birth 33 fl Fetal Learning Fetal habituation to speech sounds/dishabituation to new sounds by 32 weeks (slowed heart rate = interest) Full-term newborns prefer: Mother’s voice & smell Maybe helps to recognize mom Food they’ve experienced prenatally Music they’ve heard prenatally Words they’ve heard prenatally Stories they’ve heard prenatally (rhythm) All suggest they’ve learned something in the womb! 34 Hazards to Prenatal Development Miscarriage = spontaneous abortion Extremely common; 45%+ conceptions 6-15% of known pregnancies in Canada 25-50% of women experience miscarriage 1% recurrent (3+ consecutive) Most miscarried embryos have severe defects (aneuploidy - extra/missing chromosomes) >90% non-miscarried babies born fully healthy 35 Teratogens =any environmental agent that can potentially cause harm during prenatal development Show a dose-response relation Timing is crucial!!! Cumulative impact Individual differences matter “Fetal programming” - set up for later life (epigenetics) Dutch Hunger Winter Thalidomide poisoning Sleeper effects 36 Sensitive Periods Note: many women don’t know37 they’re pregnant until week 8! Identifying Teratogens Sleeper effects make it dif cult, but: (much) alcohol bad, particularly early Smoking bad Mercury bad Marijuana bad Fetal Alcohol Syndrome “el n” ears Some maternal eye folds diseases bad - very bad u large at upper dentate thin lips Illegal drugs bad small, widely spaced eyes 38 fl fi fi fl Maternal Factors Age (young & old moms (and dads!) put baby at risk) Nutrition (folic acid especially important) getting enough calories critical Stress-level (high stress impacts hormone environment in womb) Newborns of mothers depressed during pregnancy demonstrate different stress responses and brain activity at birth IVF studies show prenatal environment means more than genetics in in uencing child outcomes of maternal prenatal stress 39 fl SSRIs during pregnancy?? Clear negative effects of pre- and post- natal depression/anxiety on child development Associated with de cits in attention, more impulsivity, & less cognitive control Reduction in fetal brain connectivity But, should you treat with meds? Does NOT increase autism (early studies confounded) Cardiac issues? Perhaps withdrawal symptoms at birth… 40 fi Birth & The Newborn Photo by Alex Hockett on Unsplash 41 Birth 3 stages: dilation (the long period of contractions), transition/birth (pushing), afterbirth Crazy painful! Pain relieving drugs do not harm newborns nor increase C-sections but can make labour longer, & increase use of forceps Birth not painful for baby - serves important functions squeezing of head stimulates hormones to help with breathing rids amniotic uid from lungs “washes” baby in bacteria, promotes development of healthy microbiome 42 fl The Medicalization of Birth? C-sections regularly save lives of infants and mothers Yet, rates have risen steadily in the developed world, well past WHO estimated 15% that are needed (other areas too few due to lack of access) Convenient, fast, less painful… But, more allergies, more asthma, more obesity in children born via C-section Baker et al., 2022 (lack of fetal “washing”) 43 Development is Continuous Babies are not that different during nal days in womb and early days in outside world Moms who stress about birthing process hurting or otherwise traumatizing babies, etc. likely worry too much 44 fi The Newborn Eliza, ~5 mins old 45 Newborn States Alert Awake Newborn Drowsy Newborn 46 Newborn Sleep LOTS of sleep About half REM (only ~20% in adults) Autostimulation theory - brain activity during REM facilitates visual development in fetuses and newborns Myoclonic twitching - jerky movements; building sensorimotor maps 47 Sleep Techniques “sleeping through the night” a western requirement But, lots of stress about how to make it happen! More sensitive moms may have worse sleepers Babies need opportunities to self-soothe? Strongest evidence for improving sleep is “extinction” = “cry it out” (and graduated versions) No evidence for increased stress in infant nor changes in attachment 48 Crying Perfectly normal, if stressful, behaviour Increases over the rst 2 months of life Shaken Baby Syndrome can lead to head trauma/ death; correlated with crying PURPLE program to raise awareness of early intense crying periods; effective at reducing ER visits and head trauma Peak (~6 weeks), Unexpected, Resists soothing, Pain-like face, Long-lasting, Evening Colic = Inconsolable crying for more than 3 hours a day Probably gastrointestinal Usually goes away by 3-4 months 49 fi Risks to Infant Development We discussed a variety of risks to prenatal development neural tube issues, miscarriage, teratogens, maternal nutrition, age, stress- levels What are some of the risks to postnatal development? A case study of risk & outcome: NICU 50 Premature Infants This baby was 27 weeks! Anything under 34 weeks gestation (37 weeks after last period) considered premature Fetuses considered viable (>50% survival) after 24 weeks Non-viability, incidence of lifelong problems increase with earlier birth 51 Neonatal Intensive Care: Why? Babies in the NICU for a variety of reasons prematurity-related issues: immature lungs mean can’t breathe on own; jaundice Low Birth Weight (born under 5 lbs 8 oz; 2.5 kg) If LBW at full term, “small for gestational age” developmental defects that are corrected post-birth; recovery from surgery in NICU attempt to separate the why from the effects what effects does being in the NICU have on later development, irrespective of what put them there? 52 The NICU Experience Effects on Infants: A barrage of factors for which the newborn is not developmentally prepared, and which represent a (relative to non-NICU infants) signi cant change from the womb environment noise - beeping machines light - 24 hours/day pain - pin pricks, surgical cuts drugs - analgesics, antibiotics, sedatives separation from maternal interaction (touch, smell, sucking, voice) “One group of extremely low birth weight infants underwent 2–10 procedures/day between 28 and 32 weeks postconceptional age in the NICU, while a 23-week gestation baby cumulatively experienced 488 procedures during the NICU stay” 53 fi The NICU Experience Effects on Parents: Parents have little or no preparation for NICU experience Depending on level of prematurity, less prepared for the arrival of (even a healthy) infant v. Feelings of fear, grief, loss of control Life or death decisions 54 Effects of Stress on Development Brain development experience-expectant: appropriate sensory experience critical for normal development inappropriate experience (beeping, light, pain) disrupts normal patterns of neural activity - may lead to ‘hard wired’ brain abnormalities For example, early pain stimuli leads to permanent changes in the neuroendocrine system, in particular the HPA axis - regulates stress (cortisol) chronically high cortisol associated with early onset of adult diseases: atherosclerosis, hypercholesterolaemia, diabetes, cognitive impairment 55 Effects of Stress, cont. Studies with rat pups help explain effects of early pain on later development (versus the same stimuli given to adult rats, as well as non-painful stimuli given to pups) Effect depend on kind of pain: early repetitive pain (e.g. needle pricks) injury provokes ‘sprouting response’ in local sensory nerve terminals -- more pain nerves leads to hypersensitivity to pain -> decreased pain threshold As adults, increased anxiety, preference for alcohol, defensive withdrawal behaviour, & hypervigilance early prolonged pain (e.g. the result of in ammation) leads to hyposensitivity to pain -> increased pain threshold Less locomotor activity as infants As adults, stress/anxiety vulnerability & cognitive de cits 56 fl fi Outcomes for NICU Infants Some infants more sensitive to pain (often premature) even routine diaper changes noxious Some infants less sensitive (often term, but E(xtremely)LBW) therefore less likely to alert parents to pain, less likely to receive proper care for later injury Pain tolerance issues may diminish over time; some studies show effects through middle childhood 57 Speci c NICU Interventions? General awareness of the effects of stress have caused procedural changes in NICU low lighting, quiet, parent physical contact, as few procedures as possible Intervention outcomes pretty good Immediate: reduced hospital stays, decreased likelihood for physical complications Infancy: better developmental and interactional outcomes Childhood: improved cognitive, motor, attentional functioning, parental perception, quality of social interactions 58 fi Post-NICU premature/ELBW babies Regardless of effects of NICU, it is simply harder to interact with a preterm/LBW infant, who was not nished developing Attention: show less attention to novel stimuli, issues habituating (we don’t use premies in infant cognition studies) Self-regulation issues - dif cult to settle, irritable Sleep issues Mixed cues in mother-infant facial exchanges 59 fi fi Feedback loops/cascades a dif cult baby makes a worse caregiver makes a more dif cult baby makes a..... 60 fi fi Later Outcomes of Prematurity/ELBW Premature: de cits in cognition, learning disorders, attention problems, behavioral issues, motor control issues LBW (under 5.5lbs/2500g): lower IQ, ADD, ADHD, visual perception issues, anxiety, depression, low self-esteem, complex learning disabilities 61 fi “Multiple-Risk Model” = long term outcomes depend on whether had one or more than one risk factor Incidence of Psychiatric Disorders Often fall together (particularly with low SES) But, some kids resilient Intelligence, social responsiveness, high agency Responsive care from someone 62 Infant Mortality = death in the rst year 63 fi Infant Mortality = death in the rst year Risk factors: Infant mortality Preterm birth: before 36/37 Medical complications weeks Multiple birth Maternal health Low birth-weight: under Maternal age 5.5lbs/2500grams Teratogen exposure Stress Race 64 fi Birth & Race US Data Much higher in Black infants Higher in both Black (not Indigenous) and Indigenous infants 65 Birth & Race Canadian Data 20 15 Indigenous 10 5 Non- Indigenous 0 Preterm birth (per 100 births) (You want to be born later) Black infants born earlier in Indigenous infants more both countries likely to be preterm 66 Birth & Race Preterm and LBW more common amongst Black (and preterm amongst indigenous) mothers…WHY? It’s not genes Race is not a genetic category No increased risk of preterm birth amongst Black mothers in Africa (i.e., similar ancestry) 67 Birth & Race WHY? It’s not socioeconomic differences (income, education) Racial diffs in preterm birth exist even within the same SES. 68 Birth & Race WHY? Stress? The experience of racism? 69 Birth & Race Parker Dominguez et al., 2008 Studied Black and White mothers in the US What is the role of stress? Predictor measures: General stress; pregnancy stress Outcome measures: Gestational age at birth; birth weight 70 Birth & Race Parker Dominguez et al., 2008 Results Mother’s perceived racism toward themselves across lifespan predicts LBW (more racism, lower BW) Mother’s perceived racism toward others in childhood predicts LBW (more racism, lower BW) Only for Black mothers 71 Birth & Race How?? HPA axis activity Preterm birth Low birth-weight 72 Birth & Race In sum: increase instance of preterm/LBW births in Black (and, very likely, indigenous, though study not done) mothers in North America due to increased racism-related stress Your reading: Brannon (2024) volume of Black Lives Matter marches negatively correlated with both LBW and infant mortality, including in white infants (white mortality only) 73

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