A 30-year-old woman, gravida 2, para 1, at 38 weeks' gestation comes to the hospital for regular, painful contractions that have been increasing in frequency. Her pregnancy has been complicated by gestational diabetes treated with insulin. Pelvic examination shows the cervix is 50% effaced and 4 cm dilated; the vertex is at -1 station. Ultrasonography shows no abnormalities. A tocometer and Doppler fetal heart monitor are placed on the patient's abdomen. The fetal heart rate monitoring strip shows a baseline heart rate of 145/min with a variability of ≥ 15/min. Within a 20-minute recording, there are 7 uterine contractions, 4 accelerations, and 3 decelerations that have a nadir occurring within half a minute. The decelerations occur at differing intervals relative to the contractions. Which of the following is the most appropriate next step in the management of this patient?

Placement of fetal scalp electrode

A 29-year-old woman, gravida 1, para 0, at 36 weeks' gestation is brought to the emergency department after an episode of dizziness and vomiting followed by loss of consciousness lasting 1 minute. She reports that her symptoms started after lying down on her back to rest, as she felt tired during yoga class. Her pregnancy has been uncomplicated. On arrival, she is diaphoretic and pale. Her pulse is 115/min and blood pressure is 90/58 mm Hg. On examination, the patient is lying in the supine position with a fundal height of 36 cm. There is a prolonged fetal heart rate deceleration to 80/min. Which of the following is the most appropriate action to reverse this patient's symptoms in the future?

Lying in the left lateral decubitus position

Gentle compression with an abdominal binder

Lying in the supine position and elevating legs

Performing the Valsava maneuver

Fetal heart rate monitoring for USMLE Step 3: High-Yield OB/GYN Lessons

FHR Basics - The Heart of the Matter

Baseline FHR: The mean FHR during a 10-minute segment, rounded to 5 bpm increments.
- Normal: 110-160 bpm
- Tachycardia: > 160 bpm
- Bradycardia: < 110 bpm
Variability: Fluctuations in the baseline FHR that are irregular in amplitude and frequency.
- Absent: Undetectable
- Minimal: < 5 bpm
- Moderate: 6-25 bpm
- Marked: > 25 bpm
Accelerations: Abrupt, temporary increases in FHR.
Decelerations: Abrupt or gradual, temporary decreases in FHR.

⭐ Moderate variability is the single most important predictor of adequate fetal oxygenation.

Periodic Changes - Reading the Squiggles

Interpreting fetal heart rate (FHR) patterns in relation to uterine contractions is key to assessing fetal well-being.

VEAL CHOP Mnemonic for Fetal Heart Rate Patterns

Type	Onset with Contraction	Shape	Cause	Meaning
Accelerations	N/A	Abrupt peak	Fetal Movement	Okay! Reassuring.
Early Decels	Mirrors	Uniform, U-shaped	Head Compression	Benign.
Late Decels	Delayed	Uniform, U-shaped	Placental Insufficiency	Ominous (hypoxia).
Variable Decels	Abrupt, any time	Sharp, V/W-shaped	Cord Compression	Can become ominous.

Variable → Cord Compression
Early → Head Compression
Acceleration → Okay!
Late → Placental Insufficiency

⭐ A sinusoidal pattern (a smooth, undulating wave) is an ominous finding associated with severe fetal anemia or hypoxia and requires immediate intervention.

Categorization Station - Sorting the Signals

The 3-Tier System standardizes Fetal Heart Rate (FHR) interpretation for clinical action.

Category I (Normal): Strongly predictive of normal fetal acid-base status. All of the following must be present:
- Baseline FHR 110-160 bpm
- Moderate variability (6-25 bpm)
- No late or variable decelerations
Category II (Indeterminate): Any tracing not classified as Category I or III. This is a holding category.

⭐ Category II is indeterminate and the most common category, requiring continued surveillance and evaluation.
Category III (Abnormal): Predictive of abnormal fetal acid-base status. Requires prompt intervention. Includes either:
- Absent baseline variability with: recurrent late decelerations, recurrent variable decelerations, OR bradycardia.
- Sinusoidal pattern.

Rescue Maneuvers - When to Intervene

Intrauterine resuscitation is initiated for Category II or III FHR tracings to improve fetal oxygenation. Key interventions include:

Maternal Repositioning: Left lateral position to relieve aortocaval compression.
IV Fluid Bolus: Increases maternal intravascular volume and placental perfusion.
Supplemental O₂: Administered via non-rebreather mask.
Discontinue Uterotonics: Stop oxytocin to reduce uterine tachysystole.
Amnioinfusion: May be used to relieve umbilical cord compression causing recurrent variable decelerations.

⭐ If conservative measures fail to correct a Category III tracing, delivery (often via C-section) is urgently indicated.

High-Yield Points - ⚡ Biggest Takeaways

Moderate variability (6-25 bpm) is the single most important predictor of fetal well-being.

Early decelerations are benign and caused by fetal head compression.

Late decelerations are a sign of uteroplacental insufficiency and are the most worrisome pattern.

Variable decelerations, the most common type, are caused by umbilical cord compression.

A sinusoidal pattern is an ominous finding associated with severe fetal anemia.

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