Fetal Monitoring Flashcards
What is the purpose of electronic fetal monitoring (EFM)?
EFM measures the response of fetal heart rate (FHR) to uterine contractions during labor.
What are the two main types of EFM?
- External fetal monitoring (EFM)
- Internal fetal monitoring (IFM)
What are the components of internal fetal monitoring (IFM)?
- Fetal scalp electrode: Monitors FHR.
- Intrauterine pressure catheter: Measures uterine contractions.
When is internal fetal monitoring typically used?
- After membrane rupture.
- Very morbid obesity.
What is external fetal monitoring (EFM)?
A non-invasive method using external detectors to monitor:
FHR: Via an ultrasound transducer.
Uterine activity: Via a tocotransducer.
What are the advantages of external fetal monitoring (EFM)?
It avoids the need for membrane rupture and uterine invasion.
Where are the transducers placed in external fetal monitoring?
On the mother’s abdomen
What is the normal baseline fetal heart rate (FHR)?
The normal baseline FHR ranges between 110-160 beats/minute.
What is fetal bradycardia?
Fetal bradycardia is an FHR of <110 beats/minute.
What is fetal tachycardia?
Fetal tachycardia is an FHR of >160 beats/minute.
Definition of wandering baseline in FHR?
An unsteady baseline rate that wanders between 110 and 160 beats/minute.
Significance of a wandering baseline in FHR?
Rare finding suggestive of a neurologically abnormal fetus, possibly a preterminal event.
What is beat-to-beat variability?
Baseline FHR fluctuations of two cycles per minute or greater.
Interpretation of beat-to-beat variaility?
Normal variability: 6 to 25 beats/minute.
Diminished variability: May indicate a seriously compromised fetus.
What are cardiac arrhythmias in FHR?
Baseline bradycardia, tachycardia, or abrupt baseline spiking.
What does intermittent bradycardia indicates?
Often due to congenital heart block.
Types of sinusoidal heart rate pattern, and what causes it?
True sinusoidal pattern: Severe fetal anemia, caused by:
- D-isoimmunization.
- Ruptured vasa previa.
- Twin-to-twin transfusion.
Insignificant sinusoidal pattern: May follow narcotic administration, with beat-to-beat variability still >6 cycles per minute.
What are periodic fetal heart rate (FHR) changes?
Deviations from baseline FHR that are related to uterine contractions.
Definition of FHR accelerations?
Increase in FHR >15 beats/minute >15 seconds above baseline.
Causes of FHR accelerations?
- Fetal movements
- Uterine contractions
- Pelvic examination
- Fetal scalp blood sampling
Significance of FHR accelerations?
Almost always reassuring, confirming the fetus is not acidemic at that time.
Definition of FHR decelerations?
Decrease in FHR < 15 beats/minute for > 15 seconds below baseline.
Classification of FHR decelerations?
Based on timing relative to uterine contractions:
a) Early decelerations (Type I).
b) Late decelerations (Type II).
c) Variable decelerations (Type III).
What causes early decelerations (Type I), and what is their clinical significance?
Cause: Fetal head compression.
Significance: Usually benign and not associated with fetal distress, lowest point at same time with peak of contractions.
What causes late decelerations (Type II), and what is their clinical significance?
Cause: Utero-placental insufficiency.
Significance: Indicates fetal hypoxia or acidemia, requiring immediate intervention, lowestoft after peak of uterine contractions.
What causes variable decelerations (Type III), and what is their clinical significance?
Cause: Umbilical cord compression.
Significance: May be concerning if prolonged or severe.
What is an admission CTG?
A short-term cardiotocography (CTG) performed on admission to monitor fetal heart rate in low-risk pregnancies.
When is continuous EFM indicated in low-risk pregnancies?
When abnormalities in the fetal heart rate are identified during admission CTG.
What are potential complications of internal EFM electrodes?
- Fetal injuries: Scalp or eye injuries.
- Placental blood vessel injury: Leading to hemorrhage.
- Uterine perforation: From catheter placement.
- Infection risk: Increased for both mother and baby.
Why is the risk of infection higher with internal EFM?
The invasive nature of internal electrodes increases the likelihood of infection in both mother and fetus.
What is fetal scalp blood sampling.
- Fetal scalp blood is obtained with
- an illuminated fetoscope
- through the dilated cervix,
- and pH of the capillary blood is measured.
pH interpretation of fetal scalp blood sampling?
pH interpretation:
> 7.25: Reassuring; continue labor observation.
7.20-7.25: Borderline; repeat in 30 minutes.
<7.20: Repeat immediately; if acidemia is confirmed, consider immediate delivery.
What is fetal scalp stimulation, and what does it assess?
Definition: Stimulation of the fetal scalp (e.g., using Allis forceps) to observe FHR acceleration.
Significance:
- Acceleration present: Normal pH (>7.20).
- No acceleration: May indicate fetal acidemia (pH <7.20).
What is fetal pulse oximetry, and is it widely used?
Definition: Measures fetal oxygen saturation using technology similar to adult pulse oximetry.
Status: Still under evaluation before clinical adoption.
What is vibro-acoustic stimulation?
Definition: An electronic artificial larynx stimulates the fetus via the maternal abdomen to assess FHR response.
How is vibro-acoustic stimulation interpreted?
Normal: FHR acceleration >15 bpm lasting 15 seconds, occurring within 15 seconds after stimulation, with prolonged fetal movements.
Abnormal: Only 50% correlate with acidotic pH.
What is fetal electrocardiography, and what does it monitor?
Analyzes fetal ECG changes (S-T segment and P-R interval) to detect fetal hypoxia.
