Ch 5 IUGR Flashcards
Define IUGR?
Sonographic estimated fetal weight that is less than the 10th percentile
(aka fetal growth restriction)
When would we use the term “small for gestational age” (SGA)?
For newborns - defined as a neonate with a birth weight less than 10th percentile
How many infants in a low risk population will be affected by IUGR?
10%
What 2 things can cause a women to have an increased risk for IUGR up to 25% more?
-Hypertension
-Previous growth restricted infant
Growth restricted fetuses make up how much of the population?
5-8%
(can complicate 10-15% of all pregnancies)
List some risks of IUGR to the fetus?
-Intrauterine demise
-Neonatal morbidity + death
-Cognitive delays in childhood
-Diseases in adulthood
(can have lifelong effects)
What is the perinatal period?
Interval from onset of fetal viability at 24 weeks to end of neonatal period 28 days after delivery
Is fetal growth restriction (FGR) associated with stillbirths?
Yes, accounts for up to 43% of them + responsible for majority of “unexplained” stillbirths
What is the 2nd leading cause of perinatal mortality + morbidity worldwide?
IUGR
(preterm delivery is first)
Why does IUGR cause perinatal mortality + morbidity?
-Intrauterine hypoxia (not enough O2)
-Birth asphyxia (not enough O2)
-Sudden sentinel/unexpected events (such as abruption, cord prolapse or congenital anomalies)
A fetus with poor IUGR has how many times increased risk for perinatal death?
5-10x
(we do an u/s every 2 weeks for these babies b/c high risk)
What is the survival rate for fetuses under 28 weeks?
Less than 50%
List newborn affects?
-Meconium/poop aspiration
-Hypoglycemia (low blood sugar)
-Hypocalcemia (low calcium)
-Hematologic complications (blood disorders)
-Hypothermia
-Polycythemia (increased RBCs)
Why is polycythemia seen in newborns with IUGR?
B/c of increased synthesis or erythropoietin (RBC production), secondary to chronic intrauterine hypoxia
Why is hypoglycemia seen in newborns with IUGR?
-Decreased glycogen stores
-Increased sensitivity to insulin
-Decreased adipose tissue
-Decreased ability to oxidize free fatty acids + triglyceride effectively
What affects does IUGR have during childhood?
Physical, metabolic + neurologic complications:
-Learning disabilities
-Behavioral problems
-Worse performance in school
Would children affected by IUGR have higher or lower BP?
Higher
By what age do most IUGR children typically catch up on growth?
By 18 years
Fetuses below 3rd percentile tend to have what in physical appearance?
-Lower weight
-Shorter stature/height
Fetuses have a small but significant increased risk for what?
Cerebral palsy
(group of disorders that affect a person’s ability to move and maintain balance and posture)
Adults who had IUGR are at an increased risk for what?
-Acquired heart disease
-Lipid abnormalities
-Diabetes later on
What do detrimental long term intrauterine vascular changes result in?
-Hypertension
-Cerebral vascular accidents
-Diabetes
-Atherosclerosis
-Obesity
Cause of IUGR?
Half idiopathic, half multi-factorial
3 groups that RFs + etiologies are divided into?
Maternal, fetal + placental
How do we know if a fetus has IUGR or is just naturally small due to race/ethnicity?
Race: will grow at consistent rate
IUGR: not consistent + in less than 10th percentile
What condition is associated with the most severe growth deficits?
Preeclampsia
What “drug” reduces birth weight by 150-200g + is a leading cause of preventable IUGR?
Tobacco use when pregnant
Maternal medical conditions that effect blood circulation result in a decrease in what?
Uteroplacental blood flow
(conditions like hypertension, diabetes, systemic lupus erythematosus, antiphospholipid syndrome + sickle cell disease)
What is one of the m/c leading causes of IUGR?
Maternal hypertension
What 2 maternal ages can cause IUGR?
-Less than 16 y/o
-Over 35 y/o
Previous delivery of a SGA newborn showed to have what kind of maternal factors going on that influenced this?
-Low socioeconomic status (ex not eating good food)
-Use of artificial reproduction technologies
-Nicotine exposure (tobacco)
-Infection
What are the 3 m/c chromosomal abnormalities that increase a fetuses risk for IUGR?
-Trisomy 13 (patau syndrome)
-Trisomy 21 (down syndrome)
-Trisomy 18 (edwards syndrome)
50% have growth restriction with these conditions
What are other fetal factors of IUGR?
-Metabolic disorders
-Genetic syndromes
-Multiple gestations
-Congenital infections (5% of cases) such as toxoplasmosis (cat liter box) + cytomegalovirus
What type of insufficiency is associated with majority of IUGR cases?
Placental
M/c placental factor?
Alteration in uteroplacental + fetal placental circulations
What causes diminished maternal uteroplacental blood flow?
Incomplete trophoblastic invasion of spiral arteries in placental bed
Is small placental weight associated with IUGR?
Yes
Why do cord anomalies + a single umbilical artery cause an increased risk?
B/c they decrease transfer of nutrients. Such as with a velamentous cord insertion.
What does villous damage to placenta from under perfusion lead to?
Increased placental resistance + high BP
What are the 2 IUGR categories?
-Symmetric
-Asymmetric (m/c)
Difference b/w symmetric + asymmetric IUGR?
Sym:
-growth restriction in all biometric measurements, small head + abdominal size
-impairment + decrease in fetal cellular proliferation of all organs
Asym:
-growth restriction in only abdominal size when compared to head size
-large head, small abdomen (when HC to AC ratio is greater than 95th percentile)
When do symmetric + asymmetric IUGR occur in the pregnancy?
Sym: 1st or 2nd trimester
Asym: 3rd trimester
How common are symmetric + asymmetric IUGR?
Sym: 20-30%
Asym: 70-80% m/c
What category of IUGR is known as the “head sparing phenomenon”?
Asymmetric
Is symmetric + asymmetric IUGR worse?
Symmetric b/c most growth occurs in the first part of pregnancy, causing increased morbidity + mortality (unlike asymmetric)
What 3 things are markers for IUGR?
-Serum analysis
-Fundal height
-Weight percentiles
What is PAPP-A?
Hormone made by placenta in pregnancy
(pregnancy associated plasma protein - A)
Why is serum analysis a marker for IUGR? What 2 things are associated with a low birth weight?
-Increased alpha fetoprotein (AFP) is linked with increased risk of LBW
-Low PAPP-A associated with LBW
(positive predictive value of these markers are low)
What is SFH?
-Distance from top pubic symphysis to top uterine fundus (in cm)
-Should equal the gest age in weeks
After 20 weeks gest, a difference greater than how many cm is suspicious for growth restriction with SFH?
Over 3cm
Is SFH accurate?
No, often inaccurate as doctors measure wrong
(still recommended to be done with each prenatal visit after 24 weeks)
What measurements do we use to calculate weight percentiles?
BPD, HC, AC + FL
(use BC womens chart, are derived from women living at/near sea level)
Can we use growth to redate a pregnancy after its been dated by u/s after 7 weeks?
NO
How much do LBW fetuses weigh at 38-40 weeks of pregnancy?
Approx 2,510-2,750g
List 3 SF that are associated with IUGR?
-Echogenic bowel (in 2nd trimester - m/c with trisomy 21)
-Grade 3 placenta (in relation to bone)
-TRV cerebellar diameter (can be mildly reduced)
How can we make the most accurate diagnosis of IUGR?
By using multiple biometric + structural parameters
Serial growth assessments should be carried out every how many weeks?
2-4 weeks, b/c risk of false positives if done sooner
What does a nonstress test (NST) or cardiotocography measure?
FHR in response to fetal movement over time
(m/c cardiotocographic method used to assess fetal well being)
What does an abnormal FHR pattern suggest during a NST?
Heart failure
(serves as indirect measurement of CNS function)
What is considered a normal/reactive NST?
2 or more accelerations within 20 mins
What is considered an abnormal/nonreactive NST?
Lack of 2 or more accelerations in 40 mins
A BPP combines a NST with 4 biophysical features, what are they?
-Fetal movements
-Fetal tone
-Fetal breathing
-Estimate amniotic fluid volume
(each component can get up to 2 points)
Do we do biophysical profiles (BPP) on the island?
No
What would be a good BPP score?
Good: 8-10
Equivocal: 6
Need more testing: under 4
If there is not enough amniotic fluid, should BPP assessments become more frequent?
Yes, or delivery may be an option regardless of what the BPP score was
Why is the baby’s brain bigger than their abdomen with asymmetric IUGR?
B/c baby preserves their brain + takes away from the growth of the abdomen which is why it gets smaller
What does a normal middle cerebral artery doppler look like?
High peaks with no end diastolic flow
What does the ductus venosus do?
Shunts oxygenated umbilical venous blood directly to the heart
How are doppler waveforms acquired of the ductus venosus?
In TRV or SAG of fetal abdomen at level of diaphragm
(CD can help identify the DV as it branches from umbilical vein)
Explain the ductus venosus waveforms in regards to systole + diastole?
-1st peak is ventriuclar systole, 2nd peak is passive filling in ventricular diastole
-Peaks followed by a nadir (lowest point) which represents atrial contraction, known as a-waves
What would an abnormal DV waveform look like?
Decreased, absent or reversed flow in a-wave
If a fetus has an abnormal DV, does this correlate to an increased risk of perinatal mortality?
Yes, it goes from 20% to 50% if the a wave is absent or reversed as well
What does the umbilical vein do?
Transports oxygenated blood from placenta to liver
What does a normal umbilical vein doppler waveform show?
Linear forward flow
Physiologic pulsations occur in the umbilical vein until what week of gestation?
Until 13 weeks, after the pulsations are associated with fetal breathing or movement
Are pulsations of the umbilical vein that are synchronous with fetal cardiac cycle indicative of abnormal cardiac function?
Yes
Does IUGR due to placenta insufficiency cause polyhydramnios or oligohydramnios?
Oligo - may be due to decreased fetal urine + lung liquid production
(fetus has poor outcome)
How can moms manage IUGR?
-Bed rest
-Vitamins/antioxidants
-Aspirin
-Fish oil
-Hyperoxygenation
-Hypervolumic hemodilution
(none of these show significance in preventing or improving IUGR)
During what weeks of gestation is aspirin recommended?
B/w 12-16 weeks - if mom has 2 or more risk factors such as diabetes, multiple gestations, previous placental abruption or infarction
Which type of IUGR is m/c?
Asymmetric 70-80%
At what percentile is IUGR considered?
< 10%
Nonstress testing measures which 2 fetal parameters?
FHR + fetal movements
What is the leading, preventable cause of IUGR?
Maternal smoking
