Antepartum Fetal Surveillance Flashcards
1
Q
Risk factors for fetal death
A
Maternal
- Antiphospholipid syndrome
- Hyperthyroidism
- Hemoglobinopathies
- Cyanotic heart disease
- Lupus
- Chronic renal disease
- Type 1 diabetes mellitus
- Hypertensive disorders
Pregnancy-related complications
- GHTN/ pre-eclampsia*
- Oligohydramnios
- Polyhydramnios
- Decreased fetal movement
- Intrauterine (fetal) growth restriction
- Post-term pregnancy
- Isoimmunization
- Previous fetal demise
- Multiple gestation with growth discordancy
2
Q
Maternal → fetal oxygen transfer
A
Environment → Lungs → Heart → Vasculature → Uterus → Placenta → Umbilical Cord → Fetus
3
Q
Fetal effects of oxygen pathway interruption
A
Hypoxemia → Hypoxia → Metabolic Acidosis → Metabolic Acidemia → Hypotension
4
Q
Fetoplacental circulation key points
A
- Umbilical vein carries oxygenated blood to fetus
- Umbilical arteries carry deoxygenated blood to placenta
- Blood is shunted via the:
- Ductus venosus - shunts blood away from the liver (portal vein) to IVC
- Ductus arteriosus - shunts blood away from lungs (via pulmonary artery) to aorta
- Foramen ovale - shunts blood across the atrial septum (RA → LA) → more oxygenated blood to body
5
Q
What is the difference between hypoxia and hypoxemia?
A
Decreased O2 concentration in the
- Hypoxia - tissue
- Hypoxemia - blood
6
Q
Hypercapnia
A
More than the normal level of carbon dioxide in the blood
7
Q
What is the difference between acidosis and acidemia?
A
Increased hydrogen ion concentration:
- Acidemia - blood
- Acidosis - tissue
8
Q
Glucose metabolism
(aerobic vs anaerobic, biproducts)
A
- Glucose → pyruvate, no O2 needed
- Pyruvate → ATP +
- CO2 (aerobic) or
- lactic acid (anaerobic)
- does not cross placenta easily
9
Q
Fetal metabolic acidemia
A
- Pyruvic acid → lactic acid + ATP
- Buffer base consumed (HCO3, plasma proteins, Hgb, inorganic phosphate) → base deficit
- Cure: increase fetal oxgenation
10
Q
Complications of fetal acidemia
A
- Seizure disorders
- Developmental delays
- Cerebral palsy
- Fetal/neonatal death
11
Q
Neonatal encephalopathy
A
Clinically defined syndrome of disturbed neurological function in term and near term infants
- Respiratory difficulty
- Depression of tone, reflexes
- Subnormal LOC
- Often seizures
Hypoxic-ischemic encephalopathy
- a subset of neonatal encephalopathy
- result of a hypoxic/anoxic episode
- accumulation of lactic and carbonic acids (H+ ions) in the blood
12
Q
Uterine tachsystole
A
- > 5 contractions in 10 minutes averaged over 30 minutes
- Abnormal contraction pattern
- Can affect fetal oxygen exchange
13
Q
Fetal heart rate baseline
A
- FHR during a 10 minute segment rounded to nearest 5 beats, excluding periods of marked variability/periodic/episodic changes
14
Q
Normal fetal heart rate range
A
110 - 160 bpm
15
Q
Fetal tachycardia
A
Baseline > 160 bpm
16
Q
Fetal bradycardia
A
Baseline < 110 bpm
17
Q
Baseline heart rate variability
A
- Fluctuations in the FHR that are irregular in amplitude and frequency, in response to fetal environment and stimuli
- Most significant predictor of fetal well being
- Classification
- Absent - 0 bpm, or undetectable
- Minimal - detectable, 5 bpm or less
- Moderate - 6 - 25 bpm
- Marked - >25 bpm
18
Q
Sinusoidal rhythm
A
- Smooth, sine wave-like undulating pattern, usually 3-5 bpm (but can be higher) over 20 minutes.
- Not considered variability
- Reflects fetal anemia/chronic or acute bleed.
- Certain drugs can mimic.
- Rare and not good.
19
Q
Qualification of waveform
(abrupt vs gradual)
A
- Abrupt - peak to nadir is < 30 seconds
- Gradual - peak to nadir is > (or =) 30 seconds
20
Q
Periodic vs episodic FHR changes
A
- Periodic = associated with contractions
- ie early, variable, or late decelerations
- Episodic = not associated with contractions
- ie accelerations, prolonged late decels, variable decelerations
21
Q
Variable decelerations
A
- Abrupt decrease (onset to nadir < 30 sec)
- Decrease at least 15 bpm x 15 sec (up to 2 min)
- 10 bpm by 10 sec if < 32 weeks
- Baroreceptor mediated
-
Umbilical cord compression (most common in labor)
- Umbilical vein compressed → less blood returning to fetal heart → decreased preload
- Umbilical arteries compressed → higher pressure fetal heart is pumping against → increased afterload
22
Q
Late decelerations
A
- Gradual onset > or = 30 seconds
- Usually after beginning, peak and ending of contraction
- Utero-placental insufficiency → transient hypoxia during contraction → chemoreceptor → alpha adrenergic vasoconstriction → central hypertension → baroreceptor → decreased FHR
- Marginal placental O2 reserve
23
Q
Prolonged decelerations
A
- Decrease of > 15 beats/min from baseline that has a duration of > 2 minutes but < 10 minutes
- Onset may be gradual or abrupt
- Duration of > 10 minutes is considered a change in baseline
24
Q
Fetal behavioral states
(name/describe 4)
A
- Quiet sleep → stable FHR, absent to minimal variability, isolated accels w/o movement. Lasts 20 - 40 minutes
- Active sleep → wider FHR baseline and frequent accels with movement
- Quiet awake → stable, wider FHR, no accels
- Active awake → unstable FHR, large long-lasting accels, coalescence of accels/tachycardia
25
Quantification of decelerations
* Quantified by depth in beats/min and duration in minutes and seconds
* Classified as:
* _Recurrent_ - occur with \> 50% of contractions in a 20 minute window
* I**_ntermittent_** - occur with \< 50% of contractions in 20 minutes
* Bradycardia and tachycardia are quantitated in beats/min or in a range if the FHR is not stable
26
Non stress test (NST)
| (term vs preterm)
**_Term_**
* At least 2 accelerations of the FHR of 15 bpm x 15 seconds in 20 minutes of monitoring (can be as long as 40-80)
**_Preterm_**
* 24-28 wks 50% are non-reactive
* 28-32 wks – reactive = 10 bpm x 10 sec
* 15% non-reactive
* 32 weeks – reactive = 15 bpm x 15 sec (like term)
* Once reactive should stay reactive
27
Category I FHR tracings
* Normal
* Predictive of good acid/base status
* Include all of the following:
* Baseline FHR rate: 110–160 bpm
* Baseline FHR variability: moderate
* Accelerations: present or absent
* Late or variable decelerations: absent
* Early decelerations: present or absent
28
Category II FHR tracings
* Indeterminate
* _Not_ predictive of acid/base status
* *Baseline rate*:
* Bradycardia not accompanied by absent variability
* Tachycardia
* *Baseline FHR variability:*
* Minimal baseline variability
* Absent baseline variability not accompanied by recurrent decelerations
* Marked baseline variability
* Accelerations:
* Absence of induced accelerations after fetal stimulation
* *Periodic or Episodic Decelerations*:
* Recurrent variable declerations accompanied by minimal or moderate baseline variability
* Prolonged deceleration ≥2 minutes but \<10 minutes
* Recurrent late decelerations with moderate FHR baseline variability
* Variable decelerations with other characteristics, such as slow return to baseline, "overshoots," or "shoulders.”
29
Category III FHR tracings
* Abnormal
* Predictive of abnormal fetal acid-base status at time of observation
* Absent variability with:
* Recurrent late or variable decelerations
* Bradycardia
* Sinusoidal pattern
30
Potential causes of fetal tachycardia
* Maternal
* Fever
* Chorioamnionitis
* Dehydration
* Hyperthyroid
* Illicit substance use
* Medications: betasympathomimetics and parasympatholytics
* Fetal
* Anemia
* Heart failure
* Hypoxia
* Infection or sepsis
* Tachyarrhythmia
