CEFM EXAM SCRIPT FULL QUESTIONS AND
CORRECT ANSWERS REVIEW
●● True or false: continuous EFM during labor has been associated with
higher cesarean rates as opposed to IA in healthy low-risk women
Answer: • True
• There is no definitive evidence that use of intrapartum EFM leads to
significant reduction in neonatal neurologic morbidity
●● Physiological pathway of fetal oxygenation
Answer:
●● Oxygen pathway: external environment
Answer: *PO2* (partial pressure of oxygen) *declines as it moves* from
environment *to fetus*
●● Oxygen pathway: maternal lungs
Answer: • Carries oxygenated *air from external environment into
alveoli*
• From alveoli, oxygen *diffuses* across thin barrier *into pulmonary
capillary blood*
,• *Interruption* of O2 transfer *from environment to alveoli can result
from airway obstruction or CNS depression* (ex: asthma, aspiration,
apnea, narcotics, magnesium)
• *Interruptions* of O2 transfer *from alveoli to pulmonary capillary
blood can be caused by ventilation-perfusion mismatch, pulmonary
embolism, pneumonia, asthma, atelectasis, or adult respiratory distress
syndrome*
●● Oxygen pathway: maternal blood
Answer: • After *diffusing from pulmonary alveoli* into maternal blood,
approx *98% of O2 combines w Hbg in maternal RBCs* (remaining 2%
dissolves into blood)
• *Amnt of O2 bound to Hgb depends directly on PO2* as illustrated by
the oxyhemoglobin dissociation curve
●● Oxyhemoglobin dissociation curve
Answer: • Relationship between hemoglobin saturation and Po2
• In general, *tendency for Hgb to release O2 is increased by factors that
reflect an increased need for oxygen* (cellular metabolism)
●● Oxygen pathway: maternal heart
Answer: • Maternal pulmonary *veins carry oxygenated blood to the
heart* and pumped *through aorta for systemic distribution*
,• Dependent on normal cardiac function, reflected by cardiac output (HR
x SV)
• *Interruption* of O2 to fetus can be caused by *arrhythmias,
hypovolemia, compression of inferior vena cava, impaired contractility
(heart dz, diabetes, cardiomyopathy, CHF, HTN), and structural
abnormalities*
• *Most common in OB = hypovolemia*, compression of inferior vena
cava by gravid uterus
●● Oxygen pathway: maternal vasculature
Answer: Aorta → common & internal iliac arteries → anterior division
of internal iliac artery → uterine artery → arcuate arteries → radial
arteries → spiral arteries → enter intervillous space of placenta
• *Interruption* can occur w/ *hypotn* following regional anesthesia,
hypovolemia, impaired venous return, impaired cardiac output, or meds
• *Interruption* can occur w/ *vasoconstriction* in response to
endogenous vasoconstrictors or medications
• *Conditions associated with chronic vasculopathy* - CHTN, long-
standing diabetes, collagen vascular dz, thyroid dz, and renal dz
• *Pre-e* associated w abnormal vascular remodeling and can impede
perfusion
• Transient hypotension most common
●● Oxygen pathway: uterus
, Answer: • Arcuate, radial, and spiral arteries traverse muscular wall of
uterus
• *Interruption* of O2 transfer commonly *from ctx that compress
maternal blood flow in/out of intervillous space of placenta* - excessive
uterine activity, uterine stimulants (prostaglandins, oxytocin)
●● Oxygen pathway: placenta
Answer: • Facilitates *exchange of gases, nutrients, wastes, and other
molecules* between maternal blood in the intervillous space and fetal
blood in the villous capillaries
• O2 *interruptions - abruption, vasa previa, fetomaternal hemorrhage,
placental infarction, placental infection*
●● Maternal side vs fetal side of placenta
Answer: • *Maternal side* - O2 exits spiral arteries enters intervillous
space and surround chorionic villi
• *Fetal side* - paired umbilical arteries carry blood from fetus through
the umbilical cord to the placenta
●● At term, umbilical artery receives ____% of fetal cardiac output
Answer: 40%
CORRECT ANSWERS REVIEW
●● True or false: continuous EFM during labor has been associated with
higher cesarean rates as opposed to IA in healthy low-risk women
Answer: • True
• There is no definitive evidence that use of intrapartum EFM leads to
significant reduction in neonatal neurologic morbidity
●● Physiological pathway of fetal oxygenation
Answer:
●● Oxygen pathway: external environment
Answer: *PO2* (partial pressure of oxygen) *declines as it moves* from
environment *to fetus*
●● Oxygen pathway: maternal lungs
Answer: • Carries oxygenated *air from external environment into
alveoli*
• From alveoli, oxygen *diffuses* across thin barrier *into pulmonary
capillary blood*
,• *Interruption* of O2 transfer *from environment to alveoli can result
from airway obstruction or CNS depression* (ex: asthma, aspiration,
apnea, narcotics, magnesium)
• *Interruptions* of O2 transfer *from alveoli to pulmonary capillary
blood can be caused by ventilation-perfusion mismatch, pulmonary
embolism, pneumonia, asthma, atelectasis, or adult respiratory distress
syndrome*
●● Oxygen pathway: maternal blood
Answer: • After *diffusing from pulmonary alveoli* into maternal blood,
approx *98% of O2 combines w Hbg in maternal RBCs* (remaining 2%
dissolves into blood)
• *Amnt of O2 bound to Hgb depends directly on PO2* as illustrated by
the oxyhemoglobin dissociation curve
●● Oxyhemoglobin dissociation curve
Answer: • Relationship between hemoglobin saturation and Po2
• In general, *tendency for Hgb to release O2 is increased by factors that
reflect an increased need for oxygen* (cellular metabolism)
●● Oxygen pathway: maternal heart
Answer: • Maternal pulmonary *veins carry oxygenated blood to the
heart* and pumped *through aorta for systemic distribution*
,• Dependent on normal cardiac function, reflected by cardiac output (HR
x SV)
• *Interruption* of O2 to fetus can be caused by *arrhythmias,
hypovolemia, compression of inferior vena cava, impaired contractility
(heart dz, diabetes, cardiomyopathy, CHF, HTN), and structural
abnormalities*
• *Most common in OB = hypovolemia*, compression of inferior vena
cava by gravid uterus
●● Oxygen pathway: maternal vasculature
Answer: Aorta → common & internal iliac arteries → anterior division
of internal iliac artery → uterine artery → arcuate arteries → radial
arteries → spiral arteries → enter intervillous space of placenta
• *Interruption* can occur w/ *hypotn* following regional anesthesia,
hypovolemia, impaired venous return, impaired cardiac output, or meds
• *Interruption* can occur w/ *vasoconstriction* in response to
endogenous vasoconstrictors or medications
• *Conditions associated with chronic vasculopathy* - CHTN, long-
standing diabetes, collagen vascular dz, thyroid dz, and renal dz
• *Pre-e* associated w abnormal vascular remodeling and can impede
perfusion
• Transient hypotension most common
●● Oxygen pathway: uterus
, Answer: • Arcuate, radial, and spiral arteries traverse muscular wall of
uterus
• *Interruption* of O2 transfer commonly *from ctx that compress
maternal blood flow in/out of intervillous space of placenta* - excessive
uterine activity, uterine stimulants (prostaglandins, oxytocin)
●● Oxygen pathway: placenta
Answer: • Facilitates *exchange of gases, nutrients, wastes, and other
molecules* between maternal blood in the intervillous space and fetal
blood in the villous capillaries
• O2 *interruptions - abruption, vasa previa, fetomaternal hemorrhage,
placental infarction, placental infection*
●● Maternal side vs fetal side of placenta
Answer: • *Maternal side* - O2 exits spiral arteries enters intervillous
space and surround chorionic villi
• *Fetal side* - paired umbilical arteries carry blood from fetus through
the umbilical cord to the placenta
●● At term, umbilical artery receives ____% of fetal cardiac output
Answer: 40%
