A 4-month-old boy is brought to the physician for a well-child examination. He was born at 39 weeks gestation via spontaneous vaginal delivery and is exclusively breastfed. He weighed 3,400 g (7 lb 8 oz) at birth. At the physician's office, he appears well. His pulse is 146/min, the respirations are 39/min, and the blood pressure is 78/44 mm Hg. He weighs 7.5 kg (16 lb 9 oz) and measures 65 cm (25.6 in) in length. The remainder of the physical examination is normal. Which of the following developmental milestones has this patient most likely met?

Grasps small objects between thumb and finger

Transfers objects from hand to hand

Bounces actively when held in standing position

A 22-year-old primigravid woman at 41 weeks' gestation is admitted to the hospital in active labor. Pregnancy has been uncomplicated. She has asthma treated with theophylline and inhaled corticosteroids. She has had 2 surgeries in the past to repair multiple lower limb and pelvis fractures that were the result of a car accident. She is otherwise healthy. Her temperature is 37.2°C (99°F) and blood pressure is 108/70 mm Hg. Examination shows the cervix is 100% effaced and 10 cm dilated; the vertex is at -4 station, with the occiput in the anterior position. Uterine activity is measured at 275 MVUs. Maternal pushing occurs during the contractions. Fetal heart tracing is 166/min and reactive with no decelerations. Epidural anesthesia is initiated for pain relief. After 4 hours of pushing, the vertex is found to be at -4 station, with increasing strength and rate of uterine contractions; fetal heart tracing shows late decelerations. Which of the following is the most likely cause of this patient's prolonged labor?

Insufficient uterine contraction

A 27-year old primigravid woman at 37 weeks' gestation comes to the emergency department because of frequent contractions for 4 hours. Her pregnancy has been complicated by hyperemesis gravidarum which subsided in the second trimester. The contractions occur every 10–15 minutes and have been increasing in intensity and duration since onset. Her temperature is 37.1°C (98.8°F), pulse is 110/min, and blood pressure is 140/85 mm Hg. Uterine contractions are felt on palpation. Pelvic examination shows clear fluid in the vagina. The cervix is 50% effaced and 3 cm dilated. After 4 hours the cervix is 80% effaced and 6 cm dilated. Pelvic examination is inconclusive for the position of the fetal head. The fetal heart rate is reassuring. Which of the following is the most appropriate next step?

Perform external cephalic version

Perform Mauriceau-Smellie-Veit maneuver

A 28-year-old woman, gravida 2, para 1, at 40 weeks of gestation is admitted to the hospital in active labor. The patient has attended many prenatal appointments and followed her physician's advice about screening for diseases, laboratory testing, diet, and exercise. Her pregnancy has been uncomplicated. She has no history of a serious illness. Her first child was delivered via normal vaginal delivery. Her vital signs are within normal limits. Cervical examination shows 80% effacement, 5 cm dilation and softening without visible fetal parts or prolapsed umbilical cord. A cardiotocograph is shown. Which of the following options is the most appropriate initial step in management?

Administration of beta-agonists

Cardinal movements of labor for USMLE Step 2 CK: High-Yield OB/GYN Lessons

Cardinal Movements - The Fetal Descent Dance

A series of fetal position changes to navigate the maternal pelvis.

📌 Mnemonic: Every Darn Fool In Rotterdam Eats Rotten Eggs.

Engagement: Biparietal diameter passes the pelvic inlet.
Descent: Downward passage of the presenting part.
Flexion: Fetal chin tucks to chest, presenting a smaller diameter.
Internal Rotation: Fetal head rotates from transverse to anteroposterior.

⭐ The pelvic floor muscles (levator ani) are crucial for guiding the fetal head to rotate into the optimal AP diameter.
Extension: Head extends as it passes under the pubic symphysis.
External Rotation (Restitution): Head rotates back to align with the shoulders.
Expulsion: Shoulders and body are delivered.

Cardinal Movements of Labor Diagram

The 7 Movements - Every Darn Fool In Egypt Eats Raw Eggs

📌 Engagement → Descent → Flexion → Internal Rotation → Extension → External Rotation → Expulsion

7 Cardinal Movements of Labor

Engagement: The biparietal diameter (largest transverse diameter of the fetal head) passes the pelvic inlet. In nulliparous women, this often occurs before labor begins.
Descent: Continuous downward movement of the fetus through the birth canal. It's a prerequisite for all other movements.
Flexion: As the head descends, it meets resistance from the pelvic floor, causing the fetal chin to flex towards the chest. This presents the smallest head diameter (suboccipitobregmatic) for passage.
Internal Rotation: The fetal head rotates from a transverse orientation to an anteroposterior (AP) orientation, most commonly occiput-anterior (OA), to align with the longest diameter of the pelvic outlet.
Extension: Once the head reaches the level of the introitus, the occiput passes beneath the symphysis pubis. The head extends, allowing the face and chin to be born.

⭐ Asynclitism: This is the tilting of the fetal head to one side, causing the sagittal suture to be misaligned with the pelvic axis. While a mild degree is normal, persistent asynclitism can lead to labor dystocia.

External Rotation (Restitution): After delivery of the head, it rotates back to its original transverse position to align with the fetal shoulders (restitution). The shoulders then rotate into an AP position.
Expulsion: The anterior shoulder delivers under the symphysis pubis, followed by the posterior shoulder and the rest of the body.

Clinical Correlations - When the Dance Falters

McRoberts maneuver for shoulder dystocia

Failure to Progress: Arrest of descent or dilatation, often from one of three Ps: Power (contractions), Passenger (fetus), or Passage (pelvis).
- Cephalopelvic Disproportion (CPD): Mismatch between fetal head & maternal pelvis. Often requires C-section.
- Inadequate Contractions: May require oxytocin augmentation.
Malposition & Asynclitism:
- Persistent Occiput Posterior (POP): "Sunny-side up." Causes severe back labor & prolonged second stage. May require manual or instrumental rotation.
Shoulder Dystocia: OBSTETRIC EMERGENCY. Anterior shoulder impacts behind pubic symphysis after head delivery.

⭐ Associated with brachial plexus injury (Erb's palsy) and hypoxic-ischemic encephalopathy.

High‑Yield Points - ⚡ Biggest Takeaways

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