A 26-year-old primigravid woman at 39 weeks' gestation is admitted to the hospital in active labor. Pregnancy was complicated by mild oligohydramnios detected a week ago, which was managed with hydration. Her pulse is 92/min, respirations are 18/min, and blood pressure is 134/76 mm Hg. Pelvic examination shows 100% cervical effacement and 10 cm cervical dilation; the vertex is at 0 station. Cardiotocography is shown. Which of the following is the most appropriate next step in management?

Maternal repositioning and oxygen administration

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 29-year-old G2P1 at 35 weeks gestation presents to the obstetric emergency room with vaginal bleeding and severe lower back pain. She reports the acute onset of these symptoms 1 hour ago while she was outside playing with her 4-year-old son. Her prior birthing history is notable for an emergency cesarean section during her first pregnancy. She received appropriate prenatal care during both pregnancies. She has a history of myomectomy for uterine fibroids. Her past medical history is notable for diabetes mellitus. She takes metformin. Her temperature is 99.0°F (37.2°C), blood pressure is 104/68 mmHg, pulse is 120/min, and respirations are 20/min. On physical examination, the patient is in moderate distress. Large blood clots are removed from the vaginal vault. Contractions are occurring every 2 minutes. Delayed decelerations are noted on fetal heart monitoring. Which of the following is the most likely cause of this patient's symptoms?

Premature separation of a normally implanted placenta

Amniotic sac rupture prior to the start of uterine contractions

Placental implantation over internal cervical os

Chorionic villi attaching to the myometrium

Chorionic villi attaching to the decidua basalis

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 6-month-old girl presents with recurring skin infections. Past medical history is significant for 3 episodes of acute otitis media since birth. The patient was born at 39 weeks via an uncomplicated, spontaneous transvaginal delivery, but there was delayed umbilical cord separation. She has met all developmental milestones. On physical examination, the skin around her mouth is inflamed and red. Which of the following is most likely responsible for this child’s clinical presentation?

Absence of CD18 molecule on the surface of leukocytes

Umbilical cord prolapse for USMLE Step 1: High-Yield OB/GYN Lessons

Overview & Risk Factors - The Dangling Danger

Obstetric Emergency: Umbilical cord descends ahead of the presenting fetal part, risking compression & fetal hypoxia.
Core Problem: Anything preventing the fetal presenting part from snugly engaging in the pelvis after membrane rupture.
Key Risk Factors:
- Fetal: Malpresentation (breech, transverse), prematurity, multiple gestation (2nd twin).
- Uterine/Pelvic: Polyhydramnios, unengaged presenting part.
- Iatrogenic: Artificial rupture of membranes (AROM) with a high station.

⭐ High-Yield: The most common cause is iatrogenic, from artificial rupture of membranes (AROM) when the fetal head is high and not engaged in the pelvis.

Clinical Presentation & Diagnosis - Code Blue Cord

Hallmark Event: Sudden, severe fetal heart rate (FHR) changes immediately following rupture of membranes (ROM), either spontaneous or artificial.
Fetal Monitoring:
- Abrupt, prolonged fetal bradycardia (e.g., <110 bpm for >2 min).
- Severe, recurrent variable decelerations.
Definitive Diagnosis:
- Made by direct sterile vaginal examination (SVE).
- Palpation of a pulsating, rope-like structure (the umbilical cord) in the vagina or at the cervical os, ahead of the fetal presenting part.

⭐ The most common initial sign is a sudden, severe fetal bradycardia or the onset of severe, recurrent variable decelerations on fetal monitoring, especially after membrane rupture.

Fetal heart rate tracing: severe bradycardia, no recovery

Management - All Hands on Deck!

Immediate bedside actions to relieve cord compression while preparing for delivery.

Call for help! (Anesthesiology, NICU, OR staff).
Manually elevate the presenting part with a sterile-gloved hand. Keep hand in place until delivery.
Reposition mother: Knee-chest or deep Trendelenburg position.
Administer tocolytic (e.g., terbutaline 0.25 mg SC) to ↓ uterine contractions.
Discontinue oxytocin if being administered.

⭐ Pearl: The single most important initial step is to manually lift the fetal presenting part off the umbilical cord to restore fetal blood flow. This is a life-saving maneuver.

High‑Yield Points - ⚡ Biggest Takeaways

Umbilical cord prolapse is an obstetric emergency where the cord descends below the fetal presenting part.

It causes cord compression, leading to fetal hypoxia, anoxia, and potential demise.

The classic sign is sudden, severe fetal bradycardia or deep variable decelerations, typically after rupture of membranes.

Key risk factors include malpresentation (e.g., breech), an unengaged presenting part, and polyhydramnios.

Immediate management involves manually elevating the fetal head and placing the mother in the knee-chest position.

Emergency cesarean section is the definitive treatment.

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