Fetal Assessment and Prematurity Flashcards
How does the fetus respond to stress physiologically?
Peripheral vasoconstriction
Hypertension
Baroreceptor-mediated reduction in heart rate
What is the normal range for fetal heart rate?
110-160
What is fetal bradycardia?
<110
What is fetal tachycardia?
> 160
What are fetal causes of fetal bradycardia?
Asphyxia
Acidosis
What are maternal causes of fetal bradycardia?
Hypoxemia
Drugs that decrease uteroplacental perfusion
What are fetal causes of fetal tachycardia?
Hypoxemia
Arrhythmias
What are maternal causes of fetal tachycardia?
Fever
Chorioiamnionitis
Atropine
Ephedrine
Terbutaline
What range of variability should a fetal heart rate have?
6-25 bpm (excluding acceleration and deceleration)
What are factors that reduce variability?
CNS depressants
Hypoxemia
Fetal sleep
Acidosis
Anencephaly
Cardiac anomalies
What is the pathophysiology of early decelerations?
Uterine contractions compress the head > vagal stimulation > drop in FHR by <20bpm below baseline
What is the pathophysiology of late decelerations?
Decreased uteroplacental perfusion > FHR falls after peak of contraction then returns to baseline after contraction
What physical conditions may result in late decelerations?
Maternal hypotension, hypovolemia, acidosis, preeclampsia
How do late decelerations present on the monitor?
FHR gradually falls after peak of each contraction then returns to baseline after contraction
What is the pathophysiology of variable decelerations?
Umbilical compression > baroreceptor mediated reduction in FHR
How do variable decelerations present on the monitor?
Maintain variability during deceleration
Usually self-limiting
Fetal compromise prolongs FHR recovery time
What type(s) of deceleration(s) require(s) urgent assessment of fetal status d/t risk for fetal hypoxemia?
Late decelerations
Variable decelerations
What findings are consistent with Category 1 FHR assessment?
Strongly suggests normal acid- base status with not threat to fetal oxygenation:
Baseline HR between 110-160
Moderate variability
Accelerations absent or present
Early decelerations absent or present
No late or variable decelerations
What findings are consistent with Category 2 FHR assessment?
Cannot predict a normal or abnormal acid-base status:
Bradycardia without the absence of baseline FHR variability
Tachycardia
Variable variability
Absent or minimal acceleration with fetal stimulation
Recurrent variable decelerations
What findings are consistent with Category 3 FHR assessment?
Strongly suggests abnormal acid-base status with a significant threat to fetal oxygenation:
Bradycardia
Absent baseline variability
Recurrent late deceleration
Recurrent variable deceleration
Sinusoidal pattern
How is prematurity defined?
Delivery before 37 weeks gestation or less than 259 days from last menstrual cycle.
What are some risk factors for prematurity?
Multiple gestations
Premature rupture of the membranes
