4-Fetal Assessment Flashcards
What are the fetal responses to hypoxia?
Control of oxygen distribution by shunting blood flow towards vital organs( brain, heart) away from less vital (kidneys) leading to decrease level of amniotic fluid
Reduce oxygen consumption leads to decreased movement
What are the goals of antenatal testing?
To prevent fetal death through the detection of fetal hypoxia
NPV is 99.8%
PPV is 10-40%
What are the commonly used tests?
Non stress test Fetal kick counts Biophysical profiles Contraction stress test Amniotic fluid volume
What are the more specialized tests?
Umbilical artery doppler- proxy to assess the placenta. As the placenta is compromised is harder for blood to flow through
Middle cerebral artery doppler
How is the non stress test performed?
Non invasive test where external fetal doppler test is attached to the patient as well as an external tocometer
Patient is monitored for a minimum of 20 mins and the heart rate tracing is evaluated
What is the rationale behind the non stress test?
With fetal movement there is a corresponding increase in heart rate
The increase in heart rate is an indication of an intact autonomous nervous system
Abnormal test may be a sign of CNS depression
What is the interpretation of the non stress test?
Normal fetal heart rate is 110-160 bpm
At least 2 fetal HR accelerations has to be present
No fetal HR decelerations
What is the definition of the fetal heart rate acceleration?
It is based on gestational age
Before 32 weeks it is defined as 10 bpm over the baseline for 10 seconds
After 32 weeks it is defined as 15 bpm over the baseline for 15 seconds
What does an abnormal non stress test mean?
More testing required, high false positive
Can be due to a multitude of factors ( fetal sleep cycle,nicotine)
Test is an indication of fetal health at that moment in time and is usually the initial test of fetal well being when one is worried
How is the contraction stress test performed?
External heart rate monitor and tocometer is placed on patient
Contractions are initiated by use of IV oxytocin or nipple stimulation
3 contractions in 10 mins is required
Fetal heart rate tracing is then evaluated in conjunction with uterine contractions
What is the interpretation of the contraction stress?
Negative test- adequate contractions with no late or significant variable decelerations
Positive test- late deceleration follows 50% or more of the contractions
Equivocal test- everything else including inability to get the uterus to contract 3 times in 10 mins
What are the contraindications of the contraction stress test?
Anything that would compel you not to allow the patient to labor
Placenta previa
History of extensive uterine surgery
Patients at high risk for preterm labor
What is a biophysical profile?
Real time ultrasound testing looking at fetal activity and amniotic fluid levels: fetal breathing, gross movements, fetal tone, amniotic fluid volume
What to look at when doing an intra partum assessment?
Baseline Variability Acceleration Bradycardia-FHR<110 bpm Tachycardia- FHR>160 bpm Decelerations ( early, late, variable)
What is the baseline?
Mean fetal heart rate rounded to the nearest 5 bpm
Must be evaluated over a 10 mins segment
Must be present a minimum of 2 mins in the 10 min segment
