Prenatal Prenatal Development and Development and

BirthBirthChapter 4Chapter 4

Periods of Prenatal Periods of Prenatal DevelopmentDevelopment

The Period of The Period of the Zygotethe Zygote– Zygote Zygote

blastocystblastocyst– Cell Cell

differentiatiodifferentiationn

– % of % of blastocysts blastocysts that fail to that fail to implant?implant?

Periods of Prenatal Periods of Prenatal DevelopmentDevelopment

The Period of the Zygote (con’t)The Period of the Zygote (con’t)– Outer layer of blastocyst develops into:Outer layer of blastocyst develops into:

AmnionAmnion ChorionChorion PlacentaPlacenta Umbilical cordUmbilical cord

**note that these structures actually develop **note that these structures actually develop during the period of the embryoduring the period of the embryo

Periods of Prenatal Periods of Prenatal DevelopmentDevelopment

The Period of the EmbryoThe Period of the Embryo– From implantation (week 3) to week 8From implantation (week 3) to week 8– Embryonic disk is already differentiating Embryonic disk is already differentiating

into:into: EctodermEctoderm (nervous system, skin, hair, sensory (nervous system, skin, hair, sensory

receptorsreceptors MesodermMesoderm (muscles, bones, circulatory system, (muscles, bones, circulatory system,

reproductive system, excretory system)reproductive system, excretory system) EndodermEndoderm (digestive system, lungs, urinary (digestive system, lungs, urinary

tract, other internal organs)tract, other internal organs)

Periods of Prenatal Periods of Prenatal DevelopmentDevelopment

The Period of the Embryo (con’t)The Period of the Embryo (con’t)– By 4By 4thth week, heart has formed and week, heart has formed and

begun to beatbegun to beat– Becomes more human in appearance Becomes more human in appearance

during 2during 2ndnd month month– Sexual differentiation during 7Sexual differentiation during 7thth – 8 – 8thth

weeksweeks

Periods of Prenatal Periods of Prenatal DevelopmentDevelopment

The Period of the FetusThe Period of the Fetus– Final 7 months of pregnancyFinal 7 months of pregnancy– FetusFetus– Digestive and excretory systems Digestive and excretory systems

functionalfunctional– Sex detected by ultrasound by end of 3Sex detected by ultrasound by end of 3rdrd

monthmonth– Kicks and movements strong enough to Kicks and movements strong enough to

be feltbe felt– Organ systems mature rapidly during final Organ systems mature rapidly during final

3 months3 months

Periods of Prenatal Periods of Prenatal DevelopmentDevelopment

The Period of the Fetus (con’t)The Period of the Fetus (con’t)– Viable between 22-28 weeksViable between 22-28 weeks– Receives antibodiesReceives antibodies– Assume upside-down position in final Assume upside-down position in final

weeksweeks Weight of headWeight of head Shape of uterusShape of uterus

Trends in DevelopmentTrends in Development

Cephalocaudal TrendCephalocaudal Trend

Proximodistal TrendProximodistal Trend

TeratogensTeratogens Root word means “formation of Root word means “formation of

monsters”monsters” Harm isn’t always simple or Harm isn’t always simple or

straightforwardstraightforward Amount and length of exposureAmount and length of exposure Genetic makeup of mother/babyGenetic makeup of mother/baby Presence of several negative factorsPresence of several negative factors

TeratogensTeratogens

Same defect Same defect different teratogens different teratogens One teratogen One teratogen different defects different defects Some effects seen laterSome effects seen later

TeratogensTeratogens Age of babyAge of baby Sensitive periodSensitive period

TeratogensTeratogens Paternal influences often overlookedPaternal influences often overlooked

– Direct and indirect effectsDirect and indirect effects– Second hand smokeSecond hand smoke– ChemicalsChemicals– Cocaine can “hitchhike”Cocaine can “hitchhike”– Smoking, alcohol, drug use Smoking, alcohol, drug use sperm sperm– Diets low in vitamin CDiets low in vitamin C

Other FactorsOther Factors ExerciseExercise NutritionNutrition Emotional stressEmotional stress Rh blood incompatibilityRh blood incompatibility Maternal/Paternal ageMaternal/Paternal age

– Older Older less fertile, more risk of disorders less fertile, more risk of disorders– Younger Younger increased risk of prematurity, increased risk of prematurity,

infant deathinfant death

Other FactorsOther Factors

Infectious DiseasesInfectious Diseases Prenatal CarePrenatal Care Previous birthsPrevious births

Perinatal EnvironmentPerinatal Environment Environment surrounding birthEnvironment surrounding birth Stages of childbirthStages of childbirth

– ContractionsContractions– DeliveryDelivery– AfterbirthAfterbirth

Newborn appearanceNewborn appearance

Perinatal EnvironmentPerinatal Environment Assessing the NewbornAssessing the Newborn

– Apgar scaleApgar scale– 1 minute and 5 minutes after birth1 minute and 5 minutes after birth

Perinatal EnvironmentPerinatal Environment Assessing the NewbornAssessing the Newborn

– Neonatal Behavioral Assessment Scale Neonatal Behavioral Assessment Scale (NBAS)(NBAS) Several days after birthSeveral days after birth 20 inborn reflexes20 inborn reflexes Reactions to comforting and social stimuliReactions to comforting and social stimuli Unresponsiveness may indicate neurological Unresponsiveness may indicate neurological

problemsproblems Can be a parent teaching toolCan be a parent teaching tool

Perinatal EnvironmentPerinatal Environment ComplicationsComplications

– AnoxiaAnoxia Severe Severe cerebral palsy, mental retardation cerebral palsy, mental retardation Mild Mild irritability, motor/cognitive delays irritability, motor/cognitive delays Chances have been reduced with fetal Chances have been reduced with fetal

monitoringmonitoring Respiratory distress syndromeRespiratory distress syndrome

– Complicated deliveryComplicated delivery ForcepsForceps Cesarean Cesarean Medications Medications

Preterm and Small-for-DatePreterm and Small-for-Date Preterm = born more than 3 weeks Preterm = born more than 3 weeks

early, but appropriate weight for time early, but appropriate weight for time in wombin womb

Small-for-Date = underweight due to Small-for-Date = underweight due to slow fetal growthslow fetal growth– Greater risk than pretermGreater risk than preterm– Causes include smoking, drug use, stress, Causes include smoking, drug use, stress,

lack of prenatal care, multiple births, lack of prenatal care, multiple births, social supportsocial support

Postterm = born after 42 weeksPostterm = born after 42 weeks