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

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

You are a resident in the surgical ICU. One of the patients you are covering is a 35-year-old pregnant G1P0 in her first trimester admitted for complicated appendicitis and awaiting appendectomy. Your attending surgeon would like you to start the patient on moxifloxacin IV preoperatively. You remember from your obstetrics clerkship, however, that moxifloxacin is Pregnancy Category C, and animal studies have shown that immature animals exposed to fluoroquinolones like moxifloxacin may experience cartilage damage. You know that there are potentially safer antibiotics, such as piperacillin/tazobactam, which is in Pregnancy Category B. What should you do?

Wait to administer any antibiotics until you discuss your safety concerns with your attending.

Administer moxifloxacin since it is only Pregnancy Category C and, although studies may have revealed adverse effects in animals, there is no definite evidence that it causes risk in humans.

Administer piperacillin/tazobactam instead of moxifloxacin without discussing with the attending since your obligation is to "first, do no harm" and both are acceptable antibiotics for complicated appendicitis.

Discuss the adverse effects of each antibiotic with the patient, and then let the patient decide which antibiotic she would prefer.

Administer moxifloxacin since the attending is the executive decision maker and had to know the patient was pregnant when deciding on an antibiotic.

A 44-year-old woman with high blood pressure and diabetes presents to the outpatient clinic and informs you that she is trying to get pregnant. Her current medications include lisinopril, metformin, and sitagliptin. Her blood pressure is 136/92 mm Hg and heart rate is 79/min. Her physical examination is unremarkable. What should you do regarding her medication for high blood pressure?

Discontinue lisinopril and initiate labetalol

Discontinue lisinopril and initiate aliskiren

Continue her current regimen and add a beta-blocker for increased control

Discontinue lisinopril and initiate candesartan

A 28-year-old male presents to his primary care physician with complaints of intermittent abdominal pain and alternating bouts of constipation and diarrhea. His medical chart is not significant for any past medical problems or prior surgeries. He is not prescribed any current medications. Which of the following questions would be the most useful next question in eliciting further history from this patient?

"Can you tell me more about the symptoms you have been experiencing?"

"Does the diarrhea typically precede the constipation, or vice-versa?"

"Is the diarrhea foul-smelling?"

"Please rate your abdominal pain on a scale of 1-10, with 10 being the worst pain of your life"

"Are the symptoms worse in the morning or at night?"

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 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 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

Augmentation of labor for USMLE Step 1: High-Yield OB/GYN Lessons

Indications & Prerequisites - Green Light for Go-Time

Primary Indication: Labor Dystocia (abnormally slow labor).
- Protraction Disorder: Cervical dilation slower than expected.
- Arrest Disorder: No cervical change for:
  - ≥ 4 hours with adequate contractions.
  - ≥ 6 hours with inadequate contractions.
Prerequisites:
- Confirmed, term, singleton, cephalic presentation.
- Reassuring fetal status (e.g., Category I FHR).
- No clinical signs of cephalopelvic disproportion (CPD).

⭐ The most common indication for labor augmentation is arrest of the active phase of labor.

Labor curve showing protracted vs. arrested active phase

The Augmentation Toolkit - Tools of the Trade

Amniotomy (AROM):
- Artificial rupture of membranes using a sterile amnihook.
- Releases prostaglandins, promoting contractions.
- Prerequisite: Cephalic presentation, head well-engaged to prevent cord prolapse.
- ⚠️ Risks: Chorioamnionitis, umbilical cord compression.
Oxytocin (Pitocin) Infusion:
- Synthetic hormone; ↑ frequency and strength of contractions.
- Administered via IV pump for precise dose control.
- Typical dose: Start 0.5-2 mU/min, titrate every 30-60 min.
- ⚠️ Risks: Uterine tachysystole (>5 contractions in 10 min), fetal distress, uterine rupture.

⭐ High doses of oxytocin can activate vasopressin (ADH) receptors, leading to water intoxication and hyponatremia.

Artificial Rupture of Membranes (ARM) Procedure

Oxytocin Protocols - The Pitocin Playbook

Goal: Achieve adequate uterine contractions (≥200 Montevideo Units) to progress labor.
Administration: IV infusion, titrated to effect. Requires continuous fetal heart rate (FHR) and contraction monitoring.
Regimens:
- Low-Dose (Preferred): Start 0.5-2 mU/min; increase by 1-2 mU/min every 30-60 min.
- High-Dose: Start 6 mU/min; increase by 3-6 mU/min every 15-40 min. Faster, but higher risk.
⚠️ Risks:
- Uterine Tachysystole (>5 contractions in 10 min).
- Fetal distress (e.g., late decelerations).
- Water intoxication (hyponatremia).

⭐ Exam Favorite: Oxytocin is structurally similar to ADH. At high doses, it can exert an antidiuretic effect, causing water retention and dilutional hyponatremia.

Risks & Complications - Cautionary Tales

Fetal heart rate tracing with late decelerations

Uterine Tachysystole: The most common complication, leading to reduced placental blood flow.
Fetal Hypoxia & Acidosis: Consequence of tachysystole, visible as late decelerations on fetal heart rate (FHR) monitoring.
Uterine Rupture: ⚠️ A catastrophic risk, particularly in patients with a history of uterine surgery (e.g., prior Cesarean section).
Postpartum Hemorrhage (PPH): Can result from uterine atony after prolonged oxytocin exposure.
Water Intoxication: Rare, due to the antidiuretic hormone (ADH) effect of oxytocin at high doses.

⭐ Tachysystole is defined as >5 contractions in 10 minutes, averaged over a 30-minute window.

High‑Yield Points - ⚡ Biggest Takeaways

Labor augmentation addresses inadequate uterine contractions during the active phase of labor.

Oxytocin is the primary pharmacologic agent used; it requires careful, continuous fetal and maternal monitoring.

Amniotomy (AROM) can be used to augment labor, but only if the fetal head is well-engaged.

A major risk is uterine tachysystole (>5 contractions in 10 minutes), which can cause fetal distress.

Management of tachysystole includes stopping oxytocin and potential administration of a tocolytic.

Prior to augmentation, ensure no contraindications to vaginal delivery exist, such as placenta previa.

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