Fetal Growth Abnormalities

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APGO educational topic number 31 fetal
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growth abnormalities once upon a time
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there was a medical student named
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Goldilocks and she encountered three
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pregnancies during her labor and
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delivery rotation one pregnancy was big
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one pregnancy was small and the third
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pregnancy was just right in this video
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we will discuss definitions significance
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and management issues for fetal growth
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abnormalities the objectives of this
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video are to define macrosomia and fetal
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growth restriction to describe the
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ideologies of abnormal growth list
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methods of detection for fetal growth
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abnormalities describe the management of
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fetal growth abnormalities and lastly
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list the associated morbidity and
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mortality of fetal growth abnormalities
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let’s start with the pregnancy that was
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big we will discuss the definition
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significance and management issues with
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fetal macrosomia fetal macrosomia is
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defined as a very large fetus typically
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between 4,000 and 4,500 grams the
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morbidity sharply increases when the
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fetus is greater than 4,500 grams there
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are maternal and fetal causes of fetal
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macrosomia maternal factors include a
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history or macro stomach pregnancy
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pregnancy weight gain parity and glucose
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intolerance during pregnancy women with
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gestational diabetes pre gestational
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diabetes and even woman who failed their
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one-hour glucose tolerance test with the
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normal three-hour glucose tolerance test
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or at increased risk for fetal
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macrosomia there are fewer fetal factors
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that are causes for fetal macrosomia but
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these include being a male fetus and
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having beckwith Wiedemann syndrome
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moving on to significance there are
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maternal and fetal risk for the fetal
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macrosomia maternal risks include
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postpartum hemorrhage vaginal laceration
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and fetal risks include shoulder
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dystocia clavicular fracture lower Apgar
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scores and longer-term risk of being
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overweight or obese later in life the
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diagnosis of macrosomia can be
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challenging many clinicians measure the
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fundal height above the maternal
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symphysis pubis this measurement is
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commonly performed however is a poor
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predictor of fetal macrosomia and should
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be used in combination with clinical
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palpation of estimated fetal weight
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ultrasound derived estimated fetal
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weights are associated with significant
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error when the fetus is macro stomach
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and the true value of ultrasounds is in
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out macrosomia once the diagnosis of
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fetal macrosomia is made the management
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does not include induction of labor for
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this does not decrease maternal or
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neonatal morbidity and actually
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increases the c-section risk the
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American College of Obstetricians and
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Gynecologists recommends a primary
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cesarean section if an estimate of fetal
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weight is greater than 5,000 grams for a
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patient without diabetes or 4,500 grams
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for a patient with diabetes let’s now
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move to fetal growth restriction which
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describes infants whose weights are
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lower than expected the definition of
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intrauterine growth restriction or IUGR
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is when the fetus is less than the 10th
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percentile remember that this means that
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the prevalence of IUGR is approximately
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9% therefore the change in percentile
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over time may be the more important
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measurement the significance of the
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diagnosis is that the goal is to try to
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identify infants who are at risks of
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short-term and long-term morbidity or
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mortality the short-term risk so that
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small fetuses potentially lack adequate
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reserve to either continue intrauterine
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existence or potentially may lack
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reserve to undergo the stress of labor
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the long-term risk so that alterations
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and fetal growth may have lifelong
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implications it may predict health risks
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such as a cardiovascular disease insulin
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resistance and adult obesity in general
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the smaller the fetus the greater the
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risk of morbidity and mortality it’s
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important to discuss early onset IUGR
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versus late onset IUGR early in
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pregnancy fetal growth is primarily
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through cellular hyperplasia thus early
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onset IUGR can lead to irreversible
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decreases of organ size and possible
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function later in the pregnancy fetal
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growth is primarily secondary to
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cellular hypertrophy so IUGR at this
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point is more amenable to restoration of
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fetal size with adequate nutrition
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maternal factors associated with early
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onset IUGR include maternal infections
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such as rubella varicella or CMV smoking
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multiple pregnancies and chronic
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maternal disease late onset IUGR on the
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other hand is usually secondary to
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uterus until insufficiency the diagnosis
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of IUGR is similar to the diagnosis of
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macrosomia in that fundal height and
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clinical palpation of an estimated fetal
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weight
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helpful clinicians suspect IUGR
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ultrasound can be utilized to estimate
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the fetal weight in addition Doppler
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velocity of fetal vessels is very
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important in the management of IUGR the
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uterine artery systolic to diastolic
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ratio evaluates the fetal placental
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circulation as placental resistance
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increases diastolic flow decreases
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therefore there is an increase in the
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systolic and diastolic ratio absent or
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reversed end diastolic flow predicts a
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worse perinatal outcome and is usually
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an indication for delivery the middle
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cerebral artery or MCA dopplers reflects
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fetal adaptation this is because the
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fetus always tries to spare the fetal
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brain circulation when there is
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decreased placental perfusion there is
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increased mca doppler flow moving now to
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management the goal is to deliver the
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healthiest possible infant at the
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optimal time fetal surveillance is
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important with continued management of
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the pregnancy based on the results of
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fetal testing the gestational age of the
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fetus and the known risks associated
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with prematurity all need to be factored
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into the decisions regarding the timing
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of delivery and delivery should
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optimally be performed when the risk of
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fetal death is greater than the risk of
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neonatal death this concludes the aapko
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video on fetal growth abnormalities we
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have discussed the definitions
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significance and management of fetal
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macrosomia and IUGR
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you