Prenatal Development Concerns

Chapter 5

McGraw-Hill/Irwin © 2012 McGraw-Hill Companies. All Rights Reserved.

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Negative factors influencing prenatal life are believed to

be a result of genetic or environmental misfortune

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Prenatal DevelopmentFirst Two Weeks ~ Germinal Period

Release of oocyte from ovary into uterine tube

FertilizationZygote divides and moves toward the uterus - morula

Morula enters uterus and is transformed into a blastocystBlastocyst attaches to endometrium and sinks below

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Germinal Period

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Prenatal DevelopmentWEEKS 3 TO 8 ~ Embryonic Period

Zygote forms endoderm, ectoderm, and mesoderm – now called an embryo

Endoderm – digestive and respiratory systems

Ectoderm – nervous system, sensory receptors, skin

Mesoderm – circulatory, muscular, skeletal, excretory, and reproductive systems

Placenta, umbilical cord, and amnion develop

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Prenatal Period Negative factors influencing prenatal life are believed to be a result of genetic or environmental causesTeratogen

Environmental agent that causes harm to the embryo or fetusTeratogens are most dangerous between 3 and 8 weeks of gestation

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Prenatal PeriodMyth ~ maternal environment is a protective shelter for the developing embryoThalidomide - teratogen

A tranquilizing drugResponsible for causing over 500 malformed birthsMalformed arms, lack of outer ear, missing bones, some with no effects

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Prenatal Period

Weeks 9 to Birth ~ Fetal PeriodRapid body growth and organ system differentiationAt 9 weeks, fetus is 3 inches long and weighs 1 ounceAt birth, the baby will be 20 inches long and weigh 7 pounds

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Critical Periods in Human Development

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Drugs and MedicationsRecreational drugs

AlcoholCocaineTobaccoMarijuana (cannabis)

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Alcohol CDC estimates that more than 130,000 women in the US consume alcohol during pregnancy at levels known to increase birth defectsPrevalence

Use among pregnant women - 12.2%

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Fetal Alcohol Spectrum Disorders

Fetal alcohol syndrome (FAS)Cluster of birth defects resulting from prenatal alcohol exposure

Alcohol-related neurodevelopmental disorders (ARND)

Less severe symptoms

Alcohol-related birth defects (ARBD)Neonatal abstinence syndrome (NAS)

Withdrawal symptoms during neonatal period

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Fetal Alcohol Syndrome / Alcohol-Related

Neurodevelopmental Disorder

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Cocaine Effects of use during pregnancy

25% higher incidence of preterm birthFetal brain damageIncreased occurrence of miscarriageExtreme fluctuations in heart rate and blood pressure of mother and fetusConstricted blood vessels in uterusWhen born, baby is at risk for SIDS

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Cocaine “cocaine babies” exhibit mental retardation 5 times greater than that of the general populationFine and gross motor deficiencies detectable beyond 2 years of age

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Tobacco

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Tobacco

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Tobacco

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Tobacco Carbon monoxide

Interferes with hemoglobin’s oxygen carrying capacityFetal hypoxia

Nicotine Affects placental blood vessels to induce fetal hypoxia

13.8% of women smoke during pregnancy

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Cannabis (Marijuana)Little conclusive research on the effects of marijuana and its effect on the human embryo or fetusCannabis is associated with no known obstetric complicationsDrug does not alter fetal growth

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Drugs and MedicationsPrescriptive drugs

Some drugs may damage a body part that is growing and developing during the drug useSome drugs may adversely affect in the fetus that which was intended to be positively affected in the mother

Thyroid medication

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Prescriptive Medications

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Drugs and MedicationsNonprescriptive drugs

“over-the-counter” drugs (OTC)Generally considered “safe”OTC medications contain a variety of chemicals and for that reason, caution is warranted during pregnancy

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OTC MedicationsConsidered

SafePotentially Dangerous

Acetaminophen (Tylenol)

Aspirin: postterm pregnancy and prolonged labor; bleeding in skull of baby; maternal bleeding during delivery

Ibuprofen (Advil, Motrin)

Cold medications containing alcohol: FAS and ARND

Naproxen Sodium (Aleve)

OTC drugs designed to treat a variety of problems

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Drugs and MedicationsObstetrical medications

There is controversy over the use of obstetrical medicationsThese agents are known to enter fetal circulation, exerting their effects on the child, within minutes after administration to the mother

May impair fetal development

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Maternal DiseasesViral diseases

Rubella and congenital rubella syndromeHIV

Parasitic diseasesToxoplasmosis

Hematologic diseasesRh incompatibility & erythroblastosis fetalis

Endocrine diseasesDiabetes mellitus

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Rubella & Congenital Rubella Syndrome (CRS)

German measlesDamage to fetus is tied to time of maternal infection20%-50% of infected may not notice symptoms2003: 20,000 newborns had CRS

Associated defectsGrowth retardationMental retardationCongenital glaucomaCataractsBony lesionsPneumoniaHepatitisCardiac anomaliesDeafness (80%)

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Incidence of Rubella & Congenital Rubella Syndrome

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HIVHuman immunodeficiency virusEasily passed on to offspring

In utero from the mother to the fetusDuring delivery when the fetus comes in contact with infected blood or infected vaginal secretionsThrough breast milk

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Toxoplasmosis Protozoan parasites

Toxoplasma gondiiPregnant women come into contact with this parasite when cleaning a cat litter boxInfectious oocysts are in soil contaminated by cat feces

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Toxoplasmosis Consequences

Mental retardation, convulsionsMotor abnormalitiesDeafness or visual impairments

Silent infection10% of newborns show any evidence of disease

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Rh IncompatibilityRh factor on red blood cells

85% of population is Rh+Potential problem when an Rh+ man and Rh- woman conceive an Rh+ childRh+ blood cells escape fetal circulationRh+ blood cells in maternal circulation are treated as foreign bodies

Antibodies are formed to fight fetal blood cells

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Rh Incompatibility1st offspring unaffectedSubsequent offspring will illicit antibody reactionMother given anti-D IgG immunoglobulin immediately after first delivery

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Rh IncompatibilityErythroblastosis fetalis

Hemolytic disease of the newborn (HDN)Rh+ offspring exposed to maternal antibodiesCharacteristics

AnemiaImmature red blood cellsEdemaJaundice

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Neurological Deterioration in HIV-Infected Children

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Diabetes MellitusThe metabolic environment for the fetus constantly changes in utero

Normoglycemia to hypoglycemia (low blood sugar) to hyperglycemia (high blood sugar)

HyperinsulinemiaMaternal hyperglycemia in 3rd trimester leads to increases in fetal glucoseFetal insulin secretion increases

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Diabetes MellitusHyperinsulinemia

MacrosomiaIncreased insulin production increases glycogen in liver which results in triglyceride production (birth weight above 90th tile)May be responsible for adult obesity

Inhibition of maturation of lung surfactantMuscle weakness/cardiac arrhythmiasPermanent neurological damage due to neonatal hypoglycemia

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Diabetes Mellitus

Abnormalities of Infants Born to Diabetic Mothers

Spina bifidaHydrocephalusHeart defectsSkeletal and CNS defectsMacrosomia

Musculoskeletal deformitiesAsphyxiaFacial nerve injuryBrachial plexus injuryCesarean section (cephalopelvic disproportion)

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Genetic-based DisordersDown syndromePhenylketonuriaCystic fibrosisSickle cell traitSickle cell diseaseFragile X syndrome

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Down SyndromeChromosome-based disorders

Meiotic nondisjunctionOne sperm or egg cell contains two members of a particular numbered chromosome while the other member contains noneCould result in 47 chromosomesDown Syndrome

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Down SyndromeSymptoms and Signs of Trisomy 21

(Down Syndrome)

Walking delayed 1 or more yearsSlow speech development Slow development of fine motor controlToilet training delayedLower than normal birth weight

Hypotonia Short statureDelayed pubertyProne to respiratory infectionsHeart diseaseProminent anatomical features

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Down SyndromeMental retardationWalking delayed

Treadmill walking can help the child develop walking patternEmphasizes neural connectionsTrain multiple subsystems

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Phenylketonuria (PKU)Caused by a disturbance in amino acid metabolism by a gene that suppresses activity of the liver enzyme phenylalanine hydroxylase

This enzyme converts L-phenylalanine to tyrosineIf L-phenylalanine not converted, the CNS is affected

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Cystic Fibrosis (CF)Causes a thick, sticky mucus to be secreted in the lungsMucus can clog pancreas disrupting digestionPerson with CF has repeated respiratory infectionsScar tissue develops on the lungsCF drug contains enzyme to thin mucusThere is no cure

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Sickle Cell Trait (SCT)Individual inherits normal gene for hemoglobin (Hb-A) and one abnormal gene (Hb-S)

AsymptomaticLive normal livesCan pass the SCT gene to offspringNo problems with physical activity

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Sickle Cell Disease (SCD)Child inherits two abnormal Hb genes (SS)Red blood cells are sickle-shaped and can get caught in small blood vessels blocking blood flowRed blood cells are also easily destroyed or concentrate in high levels in the spleenAffects predominantly people in Africa and those of African descent

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1 of 2

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SCT

2 of 2

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Fragile X SyndromeExtra chromosome on chromosome #21Leading cause of autismDelay in motor skills

Sitting, crawling, walkingLow muscle tone, poor balance, flat feet, hyperextensibility of jointsGame playing is difficult

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Prenatal Diagnostic ProceduresOne at high risk for giving birth

Will be over 35 years at time of deliveryHas already given birth (or whose partner has) to child with genetic disease or birth defectHas a family history of genetic disease or birth defectsHas a medical history of genetic traits

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Prenatal Diagnostic ProceduresCommon procedures

UltrasoundAmniocentesisChorionic villus samplingAlpha-fetoprotein testTriple marker screening blood test

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Ultrasound SonogramCan be used to measure head size of babyHelps to determine exact length of gestationUsed to examine placement and structure of placentaCan detect baby’s gender; multiple pregnancies

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Amniocentesis

Needle inserted through abdominal wallSample of fluid from amniotic sac removedFetal cells can be tested to determine abnormalitiesUltrasound is used to guide needle placementEmployed when mother is at high risk

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Chorionic Villus Sampling (CVS)

Can detect abnormalities earlier than amniocentesis

Between 10-12 weeks of gestation

Instead of amniotic fluid, a sample of the villi of the chorion are collected and testedCarries a greater risk than amniocentesis

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Chorionic Villus Sampling (CVS)

Chorionic Villus SamplingA plastic catheter is inserted through the cervix and guided by ultrasound

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Chorionic Villus Sampling (CVS)

Chorionic Villus Sampling

A biopsy needle is inserted throughthe abdominal wall and guided by ultrasound

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Alpha-fetoprotein (AFP) TestBlood test performed at 15-20 weeks into pregnancyMeasures the amount of AFP to detect neural-tube defects (high levels) or Down Syndrome (low levels)Because of the number of false positives, it is used mainly as a screening test

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Triple Marker ScreeningTest for detecting Down Syndrome in pregnant women younger than 35 yr

Not acceptable for women older than 35 yr

The amount of human chorionic gonadotropin, unconjugated estriol, and alpha-fetoprotein (triple marker) is determined from bloodSafe with a 40%-60% accuracy rate

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Maternal NutritionSedentary women need to increase caloric intake by 300 kcal/dayActive women must make additional adjustments based upon caloric expenditureWeight gain is based upon preconception BMI

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Maternal NutritionLack of protein in maternal can lead to impaired prenatal brain growthThe developing fetal brain should achieve 25% of its mature weight prior to birthPerinatal mortality common in underweight mothers

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Maternal NutritionGrandmother effect

The second – as well as the first-generation show the elicit the effects of poor nutritionEven if a woman attains adequate nutrition throughout life, she has an increased change of giving birth to an abnormal offspring if her mother was undernourished

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Birth Weight CategoriesLow birth weightVery low birth weightExtremely low birth weight

Small for gestational age

Appropriate for gestational age

Large for gestational age

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Low Birth WeightLow birth weight: <2500 gramsVery low birth weight: <1500 gramsExtremely low birth weight: <500 grams

Low birth weight is not synonymous with premature

Is the low birth weight due to a shortened gestational period or growth retardation from malnourishment

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Small for Gestational AgeCan be born preterm (< 37 weeks) or full term (40 weeks)Inadequate nutrition in utero

Growth retardationDecreased brain development

Learning difficulties

May have low motor abilities

Parents are often concerned about SGA or LBW children involved in vigorous activities

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Appropriate for Gestational AgeEven if born weighing < 1500 grams, these babies are at less risk compared to SGAExhibit some developmental delays in weight, length, brain circumference

Catch-up by 2nd year

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Large for Gestational Age> 90th percentile for gestational ageBirth injuries are common

Brachial plexus injuriesFracture of clavicleRespiratory distress syndromeMental retardation

Diabetic mothers tend to have babies of LGA

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Maternal Health & ExercisePreeclampsia

Pregnancy induced hypertensionDeveloped in women exercising > 420 min/wkNormally, exercise reduces risk of hypertension

Gestational diabetesExercise prevents gestational diabetes

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Maternal Health & ExerciseWeight gain during pregnancy

Exercise reduces risk of weight gain

Fetal distressExtended periods of fetal bradycardia (<60 bpm)No problems associated with aerobic exercise

Preterm deliveryNo association between exercise and preterm delivery

Birth weightNo increased risk for LBW baby

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Exercise During PregnancyMaternal responses

Blood volume increases by 35% to 45%Blood shunted to muscles during exercise

Does this maternal response decrease fetal oxygen supply?

Body temperature risesCould be dangerous to the fetusFetus cannot reduce body temperature

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Exercise During PregnancyReview the exercise guidelines for exercise during pregnancy

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