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 student health coordinator plans on leading a campus-wide HIV screening program that will be free for the entire undergraduate student body. The goal is to capture as many correct HIV diagnoses as possible with the fewest false positives. The coordinator consults with the hospital to see which tests are available to use for this program. Test A has a sensitivity of 0.92 and a specificity of 0.99. Test B has a sensitivity of 0.95 and a specificity of 0.96. Test C has a sensitivity of 0.98 and a specificity of 0.93. Which of the following testing schemes should the coordinator pursue?

Test C on the entire student body followed by Test A on those who are positive

Test A on the entire student body followed by Test B on those who are positive

Test A on the entire student body followed by Test C on those who are positive

Test C on the entire student body followed by Test B on those who are positive

Test B on the entire student body followed by Test A on those who are positive

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 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 37-year-old woman, gravida 2, para 1, at 35 weeks' gestation is brought to the emergency department for the evaluation of continuous, dark, vaginal bleeding and abdominal pain for one hour. Her first child was delivered by lower segment transverse cesarean section because of a nonreassuring fetal heart rate. The patient has a history of hypertension and has been noncompliant with her hypertensive regimen. Her medications include methyldopa, folic acid, and a multivitamin. Her pulse is 90/min, respirations are 16/min, and blood pressure is 145/90 mm Hg. The abdomen is tender, and hypertonic contractions can be felt. There is blood on the vulva, the introitus, and on the medial aspect of both thighs. The fetus is in a breech presentation. The fetal heart rate is 180/min with recurrent decelerations. Which of the following is the cause of fetal compromise?

Placental tissue covering the cervical os

Rupture of aberrant fetal vessels

Induction of labor indications and methods for USMLE Step 1: High-Yield OB/GYN Lessons

Indications for Induction - Gatecrashing the Party

Maternal (Host-related)
- Post-term pregnancy (≥41 wks)
- Prelabor Rupture of Membranes (PROM)
- Hypertensive disorders of pregnancy
- Pre-gestational / Gestational diabetes
- Chorioamnionitis
- Abruptio placentae (stable)
Fetal (Guest-related)
- Intrauterine Growth Restriction (IUGR)
- Oligohydramnios
- Fetal demise
- Isoimmunization

⭐ The most common indication for induction of labor is reaching or passing the estimated due date (post-term pregnancy).

Cervical Assessment - Bishop's Green Light

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Cervical Ripening - Prepping the Runway

Goal: To soften, efface, and begin dilating an "unfavorable" cervix, assessed by the Bishop score. A score ≤ 6 suggests ripening is needed before oxytocin.
Methods:
- Mechanical:
  - Foley Catheter: Balloon inflates in the cervix, applying direct pressure.
  - Hygroscopic Dilators (Laminaria): Absorb cervical moisture and expand slowly.
- Pharmacological (Prostaglandins):
  - Misoprostol (PGE₁): Oral or vaginal administration.
  - Dinoprostone (PGE₂): Vaginal insert or gel.

Bishop Score for Cervical Ripening

⭐ Prostaglandins are contraindicated in patients with a history of major uterine surgery (e.g., classical cesarean section) due to an increased risk of uterine rupture.

⚠️ Key Risk: Uterine tachysystole.

Induction Methods - Let's Get This Started

First, assess cervical favorability using the Bishop score. A score ≥ 6 is favorable.

Cervical Ripening (for Unfavorable Cervix)
- Mechanical: Balloon catheters (Foley, Cook). Less tachysystole.
- Pharmacologic: Prostaglandins.
  - PGE1: Misoprostol (Cytotec). ⚠️ Avoid in prior C-section/uterine surgery.
  - PGE2: Dinoprostone (Cervidil).
Labor Induction/Augmentation
- Oxytocin (Pitocin): IV infusion, titrated to contraction frequency.
- Amniotomy: Artificial rupture of membranes (AROM). Must be engaged.

⭐ High-Yield: Oxytocin's primary risk is uterine tachysystole (>5 contractions in 10 min), which can cause fetal distress. Always monitor fetal heart rate and contraction pattern continuously.

High‑Yield Points - ⚡ Biggest Takeaways

Indications for induction include post-term pregnancy (>41 wks), preeclampsia, PROM, and fetal compromise.

A Bishop score ≥ 8 predicts successful induction; proceed directly to oxytocin.

An unfavorable cervix (Bishop < 8) requires ripening with prostaglandins (misoprostol) or a balloon catheter.

Oxytocin is the primary agent for induction (with a favorable cervix) and labor augmentation.

The main risk for most methods is uterine tachysystole, leading to fetal distress.

Contraindications include placenta previa, active herpes, and prior classical C-section.

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