A 27-year-old woman, gravida 2, para 1, at 37 weeks' gestation is admitted to the hospital in active labor. She has received routine prenatal care, but she has not been tested for group B streptococcal (GBS) colonization. Pregnancy and delivery of her first child were complicated by an infection with GBS that resulted in sepsis in the newborn. Current medications include folic acid and a multivitamin. Vital signs are within normal limits. The abdomen is nontender and contractions are felt every 4 minutes. There is clear amniotic fluid pooling in the vagina. The fetus is in a cephalic presentation. The fetal heart rate is 140/min. Which of the following is the most appropriate next step in management?

Administer intrapartum intravenous penicillin

Obtain vaginal-rectal swab for nucleic acid amplification testing

Obtain vaginal-rectal swab for GBS culture

Obtain vaginal-rectal swab for GBS culture and nucleic acid amplification testing

A 25-year-old woman, gravida 2, para 1, at 25 weeks' gestation comes to the emergency department because of a 1-day history of fever and right-sided flank pain. During this period, she also had chills, nausea, vomiting, and burning on urination. Her last prenatal visit was 10 weeks ago. Pregnancy and delivery of her first child were uncomplicated. Her temperature is 39°C (102.2°F), pulse is 110/min, respirations are 20/min, and blood pressure is 110/70 mm Hg. Physical examination shows costovertebral angle tenderness on the right. The abdomen is soft and nontender, and no contractions are felt. Pelvic examination shows a uterus consistent in size with a 25-week gestation. Fetal heart rate is 170/min. Laboratory studies show: Leukocyte count 15,000/mm3 Urine Nitrite 2+ Protein 1+ Blood 1+ RBC 5/hpf WBC 500/hpf Blood and urine samples are obtained for culture and drug sensitivity. Which of the following is the most appropriate next step in management?

Inpatient treatment with intravenous ceftriaxone

Outpatient treatment with oral ciprofloxacin

Inpatient treatment with intravenous ampicillin and gentamicin

Admit the patient and request an emergent obstetrical consult

A 31-year-old woman, gravida 2, para 1, at 32 weeks' gestation comes to the emergency department for sudden leakage of clear vaginal fluid. Her pregnancy has been uncomplicated. Her first child was born at term by vaginal delivery. She has no history of serious illness. She does not drink alcohol or smoke cigarettes. Current medications include vitamin supplements. Her temperature is 37.2°C (98.9°F), pulse is 70/min, respirations are 18/min, and blood pressure is 128/82 mm Hg. Speculum examination demonstrates clear fluid in the cervical canal. The fetal heart rate is reactive at 160/min with no decelerations. Tocometry shows uterine contractions. Nitrazine testing is positive. She is started on indomethacin. Which of the following is the most appropriate next step in management?

Administer betamethasone and ampicillin

Administer betamethasone, ampicillin, and proceed with cesarean section

Administer betamethasone, ampicillin, and proceed with induction of labor

Administer ampicillin and perform amnioinfusion

Administer ampicillin and test amniotic fluid for fetal lung maturity

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 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 24-year-old woman, gravida 2, para 1, at 10 weeks' gestation comes to the emergency department for vaginal bleeding, cramping lower abdominal pain, and dizziness. She also has had fevers, chills, and foul-smelling vaginal discharge for the past 2 days. She is sexually active with one male partner, and they use condoms inconsistently. Pregnancy and delivery of her first child were uncomplicated. She appears acutely ill. Her temperature is 38.9°C (102°F), pulse is 120/min, respirations are 22/min, and blood pressure is 88/50 mm Hg. Abdominal examination shows moderate tenderness to palpation over the lower quadrants. Pelvic examination shows a tender cervix that is dilated with clots and a solid bloody mass within the cervical canal. Her serum β-human chorionic gonadotropin concentration is 15,000 mIU/mL. Pelvic ultrasound shows an intrauterine gestational sac with absent fetal heart tones. Which of the following is the most appropriate next step in management?

Intravenous clindamycin and gentamicin followed by suction and curettage

Oral clindamycin followed by suction curettage

Intravenous clindamycin and gentamicin followed by oral misoprostol

Intravenous clindamycin and gentamicin followed by close observation

Oral clindamycin followed by outpatient follow-up in 2 weeks

29-year-old G2P2002 presents with foul-smelling lochia and fever. She is post-partum day three status-post cesarean section due to eclampsia. Her temperature is 101 F, and heart rate is 103. She denies chills. On physical exam, lower abdominal and uterine tenderness is present. Leukocytosis with left shift is seen in labs. Which of the following is the next best step in management?

Intravenous clindamycin and gentamicin treatment

Prophylactic intravenous cefazolin treatment

Intramuscular cefotetan treatment

Chorioamnionitis for USMLE Step 2 CK: High-Yield OB/GYN Lessons

Overview & Pathophysiology - The Fiery Womb

Intra-amniotic infection (IAI) involving the chorion, amnion, amniotic fluid, and/or placenta.
Typically an ascending polymicrobial infection from the lower genital tract, especially common after membrane rupture.
Key pathogens: Ureaplasma, Mycoplasma, GBS, E. coli, and anaerobes.

Chorioamnionitis: Maternal and Fetal Inflammatory Response

⭐ Chorioamnionitis is a leading cause of preterm labor and delivery, often triggered by the inflammatory cascade (prostaglandins) initiated by the infection.

Risk & Diagnosis - Spotting Trouble Early

Primary Risk Factors:
- Prolonged Rupture of Membranes (PROM > 18 hours)
- Long labor duration
- Multiple digital vaginal exams
- Internal fetal or uterine monitoring
- Pre-existing infections (e.g., GBS, bacterial vaginosis)
Diagnostic Criteria: Maternal Fever + ≥1 Finding
- Maternal Fever: ≥39.0°C, or 38.0-38.9°C repeated after 30 min.
- Plus one or more of the following:
  - Uterine fundal tenderness
  - Purulent or foul-smelling amniotic fluid/discharge
  - Maternal leukocytosis (>15,000 cells/mm³)
  - Fetal tachycardia (>160 bpm for at least 10 min)

⭐ In a patient with prolonged membrane rupture, the combination of maternal fever and uterine tenderness is highly specific for chorioamnionitis.

Management & Complications - Action & Aftermath

Immediate Actions
- Prompt delivery is indicated to remove the source of infection.
  - Augment labor if already in progress.
  - Induce labor if not yet started.
  - C-section for standard obstetric indications only, not for chorioamnionitis alone.
- Broad-spectrum IV antibiotics are crucial.

Complications
- Maternal: Postpartum hemorrhage (PPH) from uterine atony, endometritis, sepsis, ARDS.
- Fetal/Neonatal: Sepsis, pneumonia, meningitis, periventricular leukomalacia (PVL) → cerebral palsy.

⭐ Exam Favorite: Chorioamnionitis is a major risk factor for uterine atony, where the infected uterus fails to contract effectively after delivery, leading to potentially massive postpartum hemorrhage.

High‑Yield Points - ⚡ Biggest Takeaways

Chorioamnionitis is an ascending polymicrobial infection of the amniotic cavity, with prolonged rupture of membranes (>18 hours) as the main risk factor.

The classic presentation is maternal fever plus uterine tenderness, maternal/fetal tachycardia, or purulent cervical discharge.

Diagnosis is made clinically.

Treatment is immediate delivery (labor augmentation) and broad-spectrum IV antibiotics like ampicillin and gentamicin.

Watch for major complications like neonatal sepsis and maternal postpartum hemorrhage.

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