A 36-year-old primigravid woman at 26 weeks' gestation comes to the physician complaining of absent fetal movements for the last 2 days. Pregnancy was confirmed by ultrasonography 14 weeks earlier. She has no vaginal bleeding or discharge. She has a history of type 1 diabetes mellitus controlled with insulin. Vital signs are all within the normal limits. Pelvic examination shows a soft, 2-cm long cervix in the midline with a cervical os measuring 3 cm and a uterus consistent in size with 24 weeks' gestation. Transvaginal ultrasonography shows a fetus with no cardiac activity. Which of the following is the most appropriate next step in management?

Plan for oxytocin administration

Perform weekly pelvic ultrasound

Immediately following prolonged delivery of the placenta at 40 weeks gestation, a 32-year-old multiparous woman develops vaginal bleeding. Other than mild asthma, the patient’s pregnancy has been uncomplicated. She has attended many prenatal appointments and followed the physician's advice about screening for diseases, laboratory testing, diet, and exercise. Previous pregnancies were uncomplicated. She has no history of a serious illness. She is currently on intravenous infusion of oxytocin. Her temperature is 37.2°C (99.0°F), blood pressure is 108/60 mm Hg, pulse is 88/min, and respirations are 17/min. Uterine palpation reveals a soft enlarged fundus that extends above the umbilicus. Based on the assessment of the birth canal and placenta, which of the following options is the most appropriate initial step in patient management?

Manual exploration of the uterus

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 33-year-old woman, gravida 2, para 1, at 26 weeks' gestation comes to the emergency department because of frequent contractions. The contractions are 40 seconds each, occurring every 2 minutes, and increasing in intensity. Her first child was delivered by lower segment transverse cesarean section because of a nonreassuring fetal heart rate. Her current medications include folic acid and a multivitamin. Her temperature is 36.9°C (98.4°F), heart rate is 88/min, and blood pressure is 126/76 mm Hg. Contractions are felt on the abdomen. There is clear fluid in the vulva and the introitus. The cervix is dilated to 5 cm, 70% effaced, and station of the head is -2. A fetal ultrasound shows polyhydramnios, a median cleft lip, and fused thalami. The corpus callosum, 3rd ventricle, and lateral ventricles are absent. The spine shows no abnormalities and there is a four chamber heart. Which of the following is the most appropriate next step in management?

Perform dilation and evacuation

A 15-year-old girl is brought to the physician by her mother because of lower abdominal pain for the past 5 days. The pain is constant and she describes it as 7 out of 10 in intensity. Over the past 7 months, she has had multiple similar episodes of abdominal pain, each lasting for 4–5 days. She has not yet attained menarche. Examination shows suprapubic tenderness to palpation. Pubic hair and breast development are Tanner stage 4. Examination of the external genitalia shows no abnormalities. Pelvic examination shows bulging, bluish vaginal tissue. Rectal examination shows an anterior tender mass. Which of the following is the most effective intervention for this patient's condition?

Administer gonadotropin-releasing hormone agonist therapy

Administer oral contraceptives pills

Abnormal labor patterns for USMLE Step 2 CK: High-Yield OB/GYN Lessons

Normal Labor - The Ideal Blueprint

The 3 Ps: Labor progression is governed by Power (uterine contractions), Passenger (fetus), and Passage (pelvis).
Stage 1 (Dilation): Onset to 10 cm.
- Latent Phase: 0 to <6 cm. Gradual, variable length.
- Active Phase: ≥6 cm. Dilation: ≥1.2 cm/hr (nullipara), ≥1.5 cm/hr (multipara).
Stage 2 (Expulsion): 10 cm to delivery. <3 hrs (nullipara), <2 hrs (multipara). Add 1 hr for epidural.
Stage 3 (Placental): Delivery of infant to placenta. <30 min.

Friedman's Curve: Dilation vs. Time in Labor

⭐ The definition of active labor shifted from 4 cm to 6 cm dilation, a critical threshold for diagnosing labor abnormalities.

Labor Dystocia - The 3 'P's Problem

📌 The "3 P's" framework helps diagnose the cause of abnormal labor, or dystocia.

Power (Uterine Contractions): Inadequate strength or frequency.
- Defined as <200 Montevideo Units (MVUs) over 10 minutes.
- Management: Oxytocin augmentation.
Passenger (Fetus): Issues with the fetus.
- Size: Macrosomia (birth weight >4000-4500 g).
- Presentation/Position: Breech, face, brow, transverse lie, occiput posterior.
- Anomalies: e.g., hydrocephalus.
Passage (Pelvis/Birth Canal): Anatomic limitations.
- Pelvic Shape: Android or platypelloid pelvis.
- Cephalopelvic Disproportion (CPD): Mismatch between fetal head and maternal pelvis.
- Soft Tissue: Low-lying fibroids, cervical stenosis.

⭐ The most common cause of labor arrest in the first stage is inadequate uterine contractions (Power).

Precipitous Labor - The Express Lane

Definition: Expulsion of the fetus in < 3 hours from the onset of regular, painful contractions.
Risk Factors:
- High parity (multigravida)
- History of prior precipitous labor
- Cocaine abuse
Pathophysiology: Abnormally strong uterine contractions with low resistance from the birth canal.
Complications:
- Maternal: Uterine atony → PPH, extensive lacerations (cervical, vaginal), amniotic fluid embolism.
- Fetal: Hypoxia, intracranial hemorrhage, nerve injury (e.g., Erb's palsy).

⭐ High-Yield: The most significant maternal risk is postpartum hemorrhage (PPH) due to uterine atony from the overstimulated, exhausted myometrium.

Management Strategies - Course Correction

Conservative: Maternal repositioning, pain management, and observation.
Amniotomy (AROM): May enhance progress if membranes are intact.
Oxytocin Augmentation: For hypotonic uterine contractions (inadequate power).
- Requires continuous fetal monitoring.
- Titrate to achieve adequate contractions (>200 MVUs).
Operative Delivery:
- Cesarean Section: For arrest disorders with adequate contractions or cephalopelvic disproportion (CPD).
- Forceps/Vacuum: Option for second-stage arrest if criteria met.

⭐ If labor arrests with adequate contractions (>200 MVUs), oxytocin augmentation is inappropriate; proceed to cesarean delivery.

High‑Yield Points - ⚡ Biggest Takeaways

Abnormal labor includes protraction (slow progress) and arrest (no progress).

Etiology involves the 3 Ps: Power (inadequate contractions), Passenger (fetal malposition), or Passage (pelvic issues).

Inadequate power (<200 MVUs) is the most common cause; initial management is oxytocin.

Arrest of labor despite adequate contractions (>4 hrs with >200 MVUs) requires Cesarean delivery.

Second-stage arrest is defined by prolonged pushing (e.g., >3 hrs in a primipara with epidural).

Key risks include chorioamnionitis, postpartum hemorrhage, and fetal distress.

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Abnormal labor patterns