Antenatal Testing Flashcards
True or false: in most populations, antepartum fetal surveillance has been shown to improve perinatal outcomes
False–only a few populations have shown benefit
True or false: randomized trials have NOT been performed to determine the best antenatal test
True
How reliable are abnormal results with antenatal testing?
Often not
What is the best way to yield the most reliable results?
Using multiple modalities
What should be asked at every visit?
Fetal movement
What is the contraction stress test?
Looks at contractions, and what happens to FHT
–not used and not really reliable
Is there an optimal protocol to assess fetal movement?
No–relies on kick counts and maternal assessment of fetal movement
When do mothers feel movement? When do kick counts begin?
20 weeks
28 weeks
What is the non-stress test based on?
Based on the premise that the HR of a fetus is that is not acidotic or neurologically depressed, will temporarily accelerate with fetal movement
True or false: fetal heart reactivity is a good indicator of normal fetal autonomic function
True
What, generally, is the nonstress test? What are the two outcomes?
Check for acceleration above baseline before and after movement
Reactive (2x rxn within 20 mins)
Nonreactive (above not met w/in 40 mins)
What is the biophysical profile?
NST with 4 observations of the fetus made by real-time US
What is the umbilical artery doppler? What is this used to assess? How are results reported?
Doppler US used to assess hemodynamic components of vascular impedance, used to screen for IUGR.
Reported as a systolic /diastolic ratio
How, besides US, do you screen for IUGR? (2)
- Fundal height
- Biochemical profile (MSAFP)
Increased MSAFP increases the risk for IUGR how much?
10x
What indicates IUGR with umbilical artery doppler?
Decrease in umbilical artery diastolic flow
Who, specifically, needs antenatal screening? (4)
- IDDM
- h/o fetal demise
- Post-date pregnancies (more than 41 weeks)
- Chronic HTN
What is intrapartum fetal monitoring primarily used for? Is this done continuously or intermittently? Internally or externally
Evaluate intrapartum fetal oxygenation
Can be done either continuously or intermittently, and internally/externally
What are the two factors that are measured intrapartum?
FHT and contractions
Is intrapartum fetal monitoring a diagnostic test?
No–screening tool
Has intrapartum fetal monitoring impacted the incidence of cerebral palsy?
No
When is external monitoring used? (3)
- When clinically undesirable or impossible to rupture membranes
- NST
- Obese women
What does internal monitoring require? (2)
- Requires membranes/amnion to be ruptured
- Cervix has to be dilated 1-2 cm
What is used to assess FHR? (2)
- Electrode attached to the fetal scalp to monitor R-R intervals
- US thru abdo
What part of the head it the FSE attached to?
Anywhere, but not face or fontanelle
If the fetus is dead, but there are still electrical signals from the internal electrical FHR monitor, what does this probably represent?
Maternal electrical activity
What is the risk of infection with internal FHR?
Low
How do you monitor uterine contractions externally?
Tocodynamometer placed on the maternal abdomen, to detect alterations in the curvature of the abdomen
What are the factors that the Tocodynamometer measures?
Frequency and duration, but not amp
What is the internal device that can be used to assess contraction?
Intrauterine pressure catheter (IUPC) that is inserted after ROM
What are the risks associated with Intrauterine pressure catheter (IUPC) placement?
Small risk of perforation of the myometrium or placenta
Is there an increased risk of chorioamnionitis or postpartum endometritis with IUPC placement? If so, how much?
No
What is the normal amount of uterine contractions during labor?
5 ctx or less in 10 min avg over 30 mins
What is tachysystole? how can you tell if this is problematic?
More than 5 ctx in 10- min
qualified by presence or absence of FHR decelerations
What is the regular fetal heart rate?
110-160
Why is there a slowing HR with increased gestational age?
Fetal increased parasympathetic tone
The mean FHR is rounded to increments of what in what timeframe?
Increments of 5 bpm in a 10 min segment
When, relative to contractions, does FHR monitoring occur?
Between contractions
What defines fetal tachycardia? How long?
-10 minutes or longer of HR more than 160 bpm
What defines fetal bradycardia?
Prolonged HR less than 110
How do you quantitate fluctuations in the FHR?
As the amplitude of peak-to-peak trough in BPM
What is FHR a good indicator of, in terms of fetal physiology?
Indicator of intact integration between CNS and the fetal heart
By the time a fetus reaches (__) weeks gestation, the fetal CNS should be mature enough to produce normal variability?
28
Loss of FHR variability suggests what?
- Hypoxia
- Fetal sleep state
- CNS depressant drugs
What are the three primary mechanisms by which uterine contractions can cause a decrease in FHR?
Compression of:
- Fetal head
- Umbilical cord
- Uterine myometrial vessels
What are the two major classifications of periodic/non-periodic FHR?
Accelerations and decelerations
What are periodic changes in FHR? Non=periodic?
Periodic = FHR changes associated with contractions
Non = When fetal HR changes are not associated with contractions
What is acceleration of FHR? Deceleration?
Transient increase/decreased
What are the only 2 mechanisms that alter FHR?
- Reflex of ANS
- fetal myocardial hypoxia
What is the usual morphology of early deceleration, in relation to contractions? Is this concerning?
- Mirror image of the contractions
- not concerning-normal vagal response from compression
What causes early deceleration?
Compression by vagal stimulation from head compression
FHR never falls before what rate with early deceleration?
100 bpm
Is FHR deceleration a reassuring finding?
yes
What are late decelerations? What causes these?
Transitory decreases in FHR caused by uteroplacental insufficiency
What is the most common FHR develeration noted during labor? How do you correct these?
Variable deceleration
Move the patient to relive cord compression
How do you calculate variable decelerations?
From the onset to the nadir of the deceleration
Onset, depth, and duration of decelerations vary with what?
Successive contractions
What causes variable deceleration? When is this commonly seen?
Reflex change mediated by the vagus nerve, generally caused by umbilical cord compression.
Commonly seen with oligohydramnios
How can you relieve variable deceleration?
Changing maternal position to alleviate cord compression
What is category I classification of FHR tracings? What is this predictive of?
Normal–strongly predictive of normal acid-base status
What is category II classification of FHR tracings? What is this predictive of?
- Indeterminate
- Not predictive of abnormal fetal-acid-base status
What is category III classification of FHR tracings? What is this predictive of?
Abnormal–associated with fetal acid-base status at the time of observation
In a patient without complications, how often should FHR tracing be reviewed (first and second stages of labor)?
First stage = q 30 mins
Second stage = q 15 mins
What is the position of the mother that can help relieve cord compression?
Left lateral
What are the three major steps if intrauterine resuscitation if there is abnormal FHR?
- Stop oxytocin and startTocolysis (decrease uterine activity)
- Increase IVF to mother and fetus
- Oxygen
True or false: moderate FHR variability reliably predicts the absence of metabolic acidemia at the time of observation
True
When does intrapartum interruption of fetal oxygenation result in neurological injury?
Will not unless it progresses to metabolic acidemia
True or false: minimal absent variablity alone can reliably preduct the presece of fetal metabolic acidemia
False-does not predict
What are the four observations for the NST + biophysical profile?
- Fetal breathing
- Fetal movement
- Fetal tone
- Amniotic fluid volume
What is the crown-to-rump length used for?
Gestational age
