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Obstetrics > Fetal Growth and Development > Flashcards

Fetal Growth and Development Flashcards

1
Q

gestational age

A
  • Dated from first day of last menstrual period (LMP)
    • Precedes conception, which occurs approx 2 weeks later
  • Gestation takes approx 280 days or 10 “lunar” months or 40 weeks
    • Can quickly estimate using Nagle’s rule: +7 days to the LMP date, - 3 months = EDD
    • Only 4% of women deliver on their due date
  • Divided for convenience into trimesters
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2
Q

first trimester

A
  • The first 12 weeks from LMP (roughly 10 wks from conception)
  • 4 weeks gestation
    • CR length 4mm
    • Heart starts beating, neural folds fusing
    • Disc becomes cylindrical
    • Buds of arms, ears, legs and facial/neck structures
    • Otic pits form
  • Week five
    • Brain development, head large relative to truck
    • Primitive mouth
  • Week six
    • Nose, mouth and palate, CR=1cm
  • Week seven
    • Neck, eyelids, genital tubercle (not differentiated yet
    • Distinctly human form
  • Week eight
    • End of embryonic period, fetal period begins
    • Has or male female characteristics
  • By end of first trimester, fetus can make respiratory movements, urinate, swallow, move limbs, squint and frown and open mouth
  • Beginnings of all structures present
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3
Q

the first 2 weeks

A
  • Ovulation
  • Fertilization
    • Formation of zygote (fusion of female and male pronuclei)
    • Division of zygote into blastomere cells, then 12 cell morula
  • Formation of blastocyst (fluid filled sphere)
    • Trophoblastic cell secretes hCG to maintain corpus luteum, which secretes estrogen/progesterone to prevent menstruation
  • Implantation – upper endometrial epithelium
    • Embryonic laminar develop, start of amniotic cavity and yolk sac, the primitive respiratory/digestive system
    • 2 flat layers of cells
    • The first of 3 germ layers
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4
Q

embryonic period

A
  • Starts at third week – beginning of all major internal/external structures established
  • Day 15: first missed day of expected period
  • Trilaminar disc
    • 3 germ layers
  • Ectoderm
    • Skin of ext genitalia
    • Lower 1/3 of anal canal
    • Nervous system primitive streak->neural tube
  • Mesoderm
    • Epithelium of gonads, ureters, reproductive ducts
    • Most muscle tissue, all connective tissue
    • Lymph tissue, spleen, blood cells
    • Dermis of skin, teeth (except enamel)
  • Endoderm
    • GI tract, epithelium
    • Urinary bladder, anorectal canal
    • Male urethra, prostate gland
    • Female urethra, vaginal epithelium, vestibule
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5
Q

second trimester

A
  • Weeks 13 through 27
  • 13-15 weeks: rapid fetal growth, nails, limb movements, scalp hair pattern, head erect, eyes in position on face
  • 20-25 weeks: lanugo, eyebrows, hair, fetus hears sounds, REM, substantial weight gain, by 25 weeks, lean but well proportioned fetus. Weight 600g at 24 weeks
  • 16-18 weeks: CRL 4.5-6 inches, skeleton ossifying, 200cc amniotic fluid, brown fat forms, vernix caseosa covers skin, uterus/primordial ovarian follicles, testes beginning to descend
  • 22-24 weeks: Blink/startle responses, lungs secrete surfactant
  • Viability is reached by end of 24th week with approx. 50% survival
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6
Q

third trimester

A
  • Weeks 28 through 40
  • 26-29 weeks: eyelashes, descent of testes, weight 1050g, 37cm, lungs capable of breathing but surfactant low, survival 90% at 28 weeks.
  • 30-34 weeks: pupils respond to light, skin smooth and pink. 1700g at 32 weeks
  • 35-38 weeks: fetus orients to light, and has a firm grasp. 36 weeks – lungs mature, skin loses wrinkled appearance, head/abdomen circumferences equal, fetus start to get “plump”
  • 40 weeks – “Term” fetus averages 50 cm and 3200-3500g. Chest is prominent, breast tissue protrudes slightly. BPD 9.5 cm (hence the need for cervical dilation to 10 cm) Full term considered 37-42 weeks.
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7
Q

normal growth

A
  • Reflects the interaction of the fetus’ genetically predetermined growth potential and it’s modulation by the health of the fetus, placenta and mother
  • 3 phases
    • Cellular hyperplasia (first 16 weeks)
    • Concomitant hyperplasia and hypertrophy (weeks 16-32)
    • Cellular hypertrophy (32 weeks to term)
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8
Q

factors influencing growth rate

A
  • Poverty
  • Maternal age
  • Substances – drugs, EtoH, nicotine
  • Maternal nutrition
  • Disease
  • Psychological effects on pregnancy
  • Environmental toxins
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9
Q

evaluating fetal growth

A
  • Establish GA as early as possible
    • Using hx, LMP, early US (CRL more accurate than gestational sac diameter, yolk sac visible at 5 weeks)
    • Cardiac activity establishes GA of 5.5-6 weeks
    • Head circumference, femur length, abd circumference
    • Use of multiple markers for gestational age most accurate
    • Biometric images MOST useful for obtaining EDD in FIRST 20 weeks of pregnancy
    • After 20 weeks:
      • Monitor weight gain
      • Measure uterine size/fundal height at each visit
      • Serial US as needed
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10
Q

size-dates discrepancy

A
  • S>D
    • Inaccurate dating
    • Large for gestational age (LGA)
    • Multiple gestation
    • Polyhydramnios
    • Molar pregnancy (1st tri)
    • Uterine anomaly (fibroid)
    • Congenital anomaly
  • S<d>
    <li>Inaccurate dating</li>
    <li>Intrauterine growth restriction (IUGR)</li>
    <li>Oligohydramnios</li>
    <li>Congenital anomaly</li>
    <li>Chronic maternal disease</li>
    <li>Viral infection</li>
    </d>
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11
Q

large for gestational age (LGA)

A
  • Birth weight >90th percentile, over 4000g (8lbs 13oz) (usually above 97th percentile, reflecting infants with greatest risk of perinatal morbity/mortality. ACOG suggests >4500g
  • Macrosomia – grades 1-3 (birth weight >4000g)
  • Incidence – about 7% American babies (2008)
  • Risk factors
    • Mothers who were LGA/obese/excessive wt gain
    • GDM
    • Postdates
    • H/o large babies/previous macrosomic infant
    • Male sex
    • Race (Hispanic/African American)
    • Genetic abnormalities/syndromes (Beckwith-Wiedemann)
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12
Q

LGA complications

A
  • Cephalopelvic disproportion (CPD)
    • Labor dystocia/prolonged labor
    • Shoulder dystocia, birth injuries
    • Maternal soft tissue damage/lacerations
    • Increased C/S
  • Postpartum hemorrhage
  • Stillbirth, esp with grade 3 macrosomia (5000g)
  • Neonatal complications
    • Low Apgar, need for mechanical ventilation, RDS
    • Hypoglycemia, perinatal asphyxia
    • Hematologic abnormalities/polycythemia
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13
Q

prenatal managment and prognosis of LGA

A
  • Prenatal Management
    • Screen for GDM if not already done
    • US to r/o polyhydramnios, molar pregnancy, fibroids
    • Serial US to monitor growth
    • Anticipate cephalopelvic disproportion (CPD) and sequelae
    • Anticipate shoulder dystocia
    • Anticipate postpartum hemorrhage
    • Offer delivery at 38 wks if possible macrosomia
    • Offer elective C/S
    • Alert peds at delivery
  • Prognosis
    • Risk of subsequent LGA baby
    • Increased risk of diabetes eventually in child
    • Neonatal complications and sequelae
    • Increased risk of obesity, insulin resistance, hyperlipidemia, CV disease? in child
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14
Q

IUGR

A
  • Intrauterine Growth Restriction/FGR (Fetal Growth Restriction)
    • Impaired or restricted intrauterine growth
    • Significant because there is an inverse relationship between fetal/neonatal weight percentile and perinatal mortality
    • Not to be confused with small-for-gestational age (SGA)
      • Neonatal diagnosis of size below the 10th percentile
        • Usually genetic or due to inadequate nutrition
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15
Q

IUGR risk factors

A
  • Poor nutrition/weight gain
  • Vascular disease/HTN
  • Renal disease
  • Infection
  • Genetic abnormality
  • Multiple gestation
  • Placental problems
  • Pregestational diabetic
  • Drug use/smoking/EtoH
  • Hypoxemia/anemia
  • Late onset prenatal care
  • Low SES
  • Prothrombotic disorders
  • ART
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16
Q

IUGR: symmetrical, asymmetrical, complications

A
  • Symmetrical (20-25%) “global growth restriction”
    • Compromised growth in length, head circumference and weight
    • More likely to have permanent neuro sequelae
    • TORCH infections
    • Chromosomal abnormalities
    • Substance abuse
  • Asymmetrical (70%)
    • Decreased length and weight, but normal head circumference aka head-sparing (lack of fat, normal growth first 2 trimesters)
    • HTN, malnutrition, Pre-eclampsia
  • Complications
    • Increased risk fetal distress
    • Meconium staining
    • Increased perinatal morbidity and mortality
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17
Q

IUGR causes

A
  • Maternal: Poor weight gain, anemia, drugs/EtoH, smoking, HTN, GD, celiac disease, poor nutrition
  • Uteroplacental: Pre-eclampsia, multiple gestation/Twin to twin transfusion syndrome (TTTS), uterine malformations, placental insufficiency
  • Fetal: vertically transmitted infections, chromosomal abnormalities
18
Q

IUGR diagnosis and management

A
  • Diagnosis
  • Careful menstrual/medical/OB hx
  • Accurate dating/early ultrasound
  • Monitor for adequate weight gain
  • Carefully evaluate fundal height changes
    • Watch for “progressive” growth
    • <2cm in 4 wks is suspicious
    • If possible, single, consistent examiner
  • 2 U/S 4 wks apart to confirm
    • Esp head and abdominal circumference
    • AFI check to r/o oligohydramnios
  • Management
    • Limit activity/bed rest
    • Nutrition
    • Cessation of smoking
    • Fetal surveillance
      • Repeat U/S q 4-6 wks
      • Non Stress Tests (NST) weekly
      • Biophysical Profiles (BPP) prn
      • Amniocentesis for lung maturity
    • Delivery of compromised fetus
19
Q

birth defects/congenital malformations

A
  • A major birth defect is one of medical, surgical or cosmetic significance
    • Prevalence 2-4% among live born infants
    • May be isolated or multiple, major or minor
    • Genetic and environmental factors play a role
    • Maternal age
    • Illness
    • Drug use
    • Physical features of uterine environment
20
Q

etiology of birth defects

A
  • Unknown causes (65-75%)
  • Genetic
    • Single gene disorders (15-20%)
    • Chromosomal abnormalities (5%)
  • Environmental exposures (10%)
    • Maternal illness, substance use, infection, drugs, chemicals, radiation, hyperthermia, mechanical/physical constraints
21
Q

genetic disorders

A
  • >90% do not survive to term
  • Multiple organ systems tend to be involved
  • Longevity and fertility of these individuals tend to be reduced
  • Chromosomal Abnormalities
    • Affect 1 in 200 newborn infants
    • Nondisjunction, unequal recombination, inversions, deletions/duplications, translocations
  • Single gene disorders
    • Autosomal dominant/recessive, X-linked
  • Non-Mendelian patterns of inheritance
    • Unstable DNA, fragile X syndrome, imprinting, mitochondrial inheritance, etc.
22
Q

teratogens

A
  • Study of malformations - teratology
  • Genetic (single gene and chromosomal abnormality) 20%
  • Environmental factors 10%
  • Unknown 70%
  • Timing of exposure, dose and duration all influence effect on fetus
  • First two weeks after conception known as “all or none period”
  • Organogenesis (menstrual weeks 5-10) – tissues are differentiating, susceptible to teratogenic effects
  • causes:
    • Ionizing radiation
    • Other meds: ACE inhibitors, chloramphenicol, warfarin/
      • anticoags, DES, toluene, iodides, lithium, accutane/iso-retinoin, tetracycline, thalidomide, valproate, lead, rubella vaccine, anticonvulsants, antineoplastics
    • SSRIs
    • Avoid: ibuprofen, ASA, sulfa drugs at term, trimethoprim
    • Always check drug class
      • A, B, C usually OK, especially if benefit outweighs risk
    • EtoH, tobacco, recreational drugs
23
Q

maternal illness

A
  • Pregestational diabetes -2-3 fold increase in congenital anomalies (esp heart disease, spina bifida)
    • Abnormal fetal growth
    • Newborn hypoglycemia
    • Stillbirth
  • Phenylketonuria
    • Microcephaly, MR, congenital heart disease
  • Androgen producing tumors - Virilization of female fetuses
  • Autoimmune diseases - Same or different toxicity to fetus
    • SLE – fetal, not maternal heart block
    • Treatment of mother does not always reduce effects on fetus
  • Influenza – 2nd trimester assoc. w/cleft lip, NTD, congenital heart defects, hydrocephaly
24
Q

infectious teratogens

A
  • Infections (TORCH) can cause malformations/congenital infections, disability and death
    • Toxoplasmosis
    • Other (syphilis and parvovirus)
    • Rubella
    • Cytomegalovirus (CMV)
    • Herpes/varicella
25
Q

nonspecific sonographic signs suggestive of fetal infection

A
  • Microcephaly
  • Cerebral or hepatic calcifications
  • IUGR
  • HSM
  • Cardiac malformations, limb hypoplasia, hydrocephalus
  • Hydrops – edema of the baby
27
Q

alcohol

A
  • 60% of women have at least 1 drink per year
  • Of those who drink 13% have more than 7 drinks per week
  • 7.6% of pregnant women in US use EtoH and 1.4% admit to binge drinking (2010 CDC)
  • Non pregnant women – 52% use EtoH, 15% admit to binging
  • NO AMOUNT OF ALCOHOL IS CONSIDERED SAFE IN PREGNANCY (US Surgeon General and Secretary HHS)
28
Q

alcohol use in pregnancy

A
  • There is no exact dose-response relationship between the amount of EtoH consumed during the perinatal period and the exact damage caused by EtoH to the infant
  • Binge drinking exerts a potentially greater negative effect than comparable consumption of EtoH over several days
  • Other factors that effect outcome and increase risk of fetal alcohol syndrome (FASD)
    • Maternal age
    • High parity
    • Being African-American or Native American
    • Genetics
  • EtoH freely crosses the placenta
  • Fetal BAL approach maternal levels within two hours of maternal intake
  • Elimination relies on maternal metabolic capacity, which varies – this explains why similar amounts of EtoH result in wildly varying phenotypic presentations in infants
  • EtoH is a teratogen with the potential to cause deleterious effects at all stages of gestation, the most severe being fetal alcohol spectrum disorder (FASD) and stillbirth.
29
Q

exposure risk factors

A
  • The following increase the risk of FASD:
  • Low economic status
  • Smoking
  • Unmarried
  • Unemployed
  • Illicit drug use
  • H/o sexual or physical abuse
  • H/o incarceration
  • Family member who drinks heavily
  • Socially transient
  • Psychological stress/mental health disorder
30
Q

etoh effects on fetus

A
  • Fetal alcohol spectrum disorder (FASD) describes the broad range of adverse sequelae
    • No effect, normal
    • Fetal alcohol effects (FAE)
    • Alcohol related birth defects (ARBD)
    • Fetal alcohol syndrome (FAS)
31
Q

tobacco use in pregnancy

A
  • The most important modifiable risk factor associated with adverse outcomes
  • Estimated that cessation during pregnancy could prevent:
    • 10% of perinatal deaths
    • 35% of low birth weight infants
    • 15% of preterm deliveries
32
Q

pathophysiology of tobacco use in pregnancy

A
  • Impaired fetal oxygen delivery
    • Placentas of smokers show structural changes that may contribute to abnormal gas exchange
  • Carbon monoxide exposure
    • Carboxyhemoglobin clears slowly from fetal circulation and diminishes tissue oxygenation
  • Direct damage to fetal genetic material, genetic susceptibility varies
  • Direct toxicity form more than 2500 substances found in cigarettes, up to 100,000 compounds in tobacco smoke!
  • Directly impairs lung development
  • Sympathetic activation leads to accelerated heart rate/ reduction in fetal breathing movement
33
Q

adverse effects of tobacco use in pregnancy

A
  • Infertility (maternal)
  • Low birth weight (LBW) <2500g
  • Miscarriage
  • Stillbirth, including from second hand smoke
  • Preterm premature rupture of membranes
  • Placental abruption/previa
  • Preterm delivery (1.3-2.5 times more likely)
  • Congenital malformations, likely
  • Postnatal morbidity
  • Preeclampsia
  • Decreased milk volume production, postnatal morbidities (SIDS, respiratory infections, asthma, atopy…)
  • ?long term implications for offspring: DMII, reduced sperm concentration, dyslipidemia, cancer
34
Q

smoking cessation in pregnancy

A
  • Pregnancy provides a unique opportunity for medical intervention for smoking cessation because of the frequency of prenatal visits
  • The five As: Ask, Advise, Assess, Assist, Arrange
  • 800-QUIT-NOW, CBT, hypnotherapy, acupuncture
  • Pharmacotherapy – women who are otherwise unable to quit or heavy smokers (>10day) – In this population, the benefits of quitting with pharmacotherapy outweigh the potential risks of pharmacotherapy and continued smoking.
  • Lowest dose necessary, avoid in first trimester
  • Nicotine replacement therapy and bupropion (Cat C) are first line
35
Q

opiates

A
  • 50% of US women who use drugs are of childbearing age
  • 25% of these use heroin
  • Some exposure risks are same for pregnant and nonpregnant women
    • Infection, psychological stress, violence
36
Q

s/sx of high-risk chemical abuse

A
  • Late to prenatal care
  • Multiple missed appointments
  • Impaired school/work performance
  • Past OB h/o SAB, IUGR, premature birth, placental abruption, stillbirth, precipitous delivery
  • Children w/ neuro-developmental problems
  • H/o drug/EtoH problems
37
Q

obstetrical complications from opiate use in pregnancy

A
  • Preeclampsia
  • Placenta abruption
  • Premature labor/delivery
  • Placental insufficiency
  • Third trimester bleeding
  • Malpresentation
  • Nonreassuring fetal status
  • Meconium passage
  • Low birth weight
  • Perinatal mortality
  • Puerperal morbidity
38
Q

neonatal outcomes from opiate use

A
  • Premature birth
  • Neonatal opiate withdrawal
  • Postnatal growth deficiency
  • Microcephaly
  • Neurobehavioral deficits- tremors, high pitched cry, excess suck, hyper-alertness, irritability
  • SIDS
  • Post natal effects – difficult to ascertain long-term effects due to confounding variables (psychosocial factors, exposure to other drugs prenatally, prematurity, IUGR)
39
Q

cocaine use in pregnancy

A
  • Less women than men use the drug but numbers are growing
    • Especially with crack cocaine use
  • Effects related to dose and stage of pregnancy
    • Decreased birth weight, length and head circumference
    • Increased risk prematurity, placental abruption, SAB, fetal death
    • Readily crosses placenta
  • Major mechanism of fetal and placental damage is vasoconstriction
  • Teratogenic effects not definitely established
    • possibly intestinal atresia, brain anomalies
  • Cognitive development of children exposed in utero controversial
  • Maternal cocaine use tests positive in neonatal urine within 2 days of delivery and is excreted within 12-24 hrs
    • Meconium stays positive for 3 days and hair for months
40
Q

marijuana use in pregnancy

A
  • Most commonly used illicit substance taken during pregnancy
  • Impact unknown
    • Not significantly related to any growth measures at birth, prematurity or congenital anomalies
  • May be associated with EtoH and cigarette use
  • In a retrospective study of 417 mothers who reported ONLY marijuana use in pregnancy, there was no association between MJ use and prematurity or congenital anomalies
  • Heavy users had a trend toward a slight decrease in birth weight
41
Q

methamphetamine use during pregnancy

A
  • 10 million Americans have tried methamphetamine at some point in their lives
    • A neurotoxic agent that damages ending of brain cells containing dopamine
    • 3.5 times more likely to be SGA
    • No fetal structural abnormality has been associated definitively with perinatal amphetamine exposure
42
Q

management of pregnant substance user

A
  • Screen all pregnant women for EtoH and substance use
  • Counsel regarding risks of specific substance used
  • Use behavioral therapy and/or pharmacotherapy to treat addiction
  • Assemble a multidisciplinary team of providers (including social workers and peds) to comprehensively assess the patient and her baby
  • Test for STIs and treat
  • Schedule frequent visits to monitor maternal and fetal status
  • Obtain early US to confirm GA and establish accurate baseline for growth
  • Begin antepartum fetal surveillance if there is evidence of pregnancy complications
  • Inform peds of possibility of neonatal withdrawal
  • Discourage breastfeeding in women who continue to take illicit drugs
  • Address the needs of poorly nourished, homeless and or incarcerated pregnant substance abusers
  • Education about nutrition and weight gain
  • Referral to food assistance programs, shelters, vouchers for transportation, prenatal multivitamins
  • Consult anesthesia prior to delivery to develop pain management plan (opioid use assoc. with more pain sensitivity, may require higher doses, difficult venous access

Obstetrics (14 decks)

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