A 4-week-old infant is brought to the physician by his mother because of blood-tinged stools for 3 days. He has also been passing whitish mucoid strings with the stools during this period. He was delivered at 38 weeks' gestation by lower segment transverse cesarean section because of a nonreassuring fetal heart rate. He was monitored in the intensive care unit for a day prior to being discharged. His 6-year-old brother was treated for viral gastroenteritis one week ago. The patient is exclusively breastfed. He is at the 50th percentile for height and 60th percentile for weight. He appears healthy and active. His vital signs are within normal limits. Examination shows a soft and nontender abdomen. The liver is palpated just below the right costal margin. The remainder of the examination shows no abnormalities. Test of the stool for occult blood is positive. A complete blood count and serum concentrations of electrolytes and creatinine are within the reference range. Which of the following is the most appropriate next step in management?

Continue breastfeeding and advise mother to avoid dairy and soy products

Perform stool antigen immunoassay

Perform an air enema on the infant

Assess for IgA (anti‑)tissue transglutaminase antibodies (tTG)

Stop breastfeeding and switch to soy-based formula

A 25-year-old man presents with abdominal pain and bloody diarrhea. His symptoms have been recurrent for the past few months, and, currently, he says he is having on average four bowel movements daily, often bloody. He describes the pain as cramping and localized to the left side of his abdomen. He also says that he has lost around 4.5 kg (10 lb) over the past 3 months. There is no other significant past medical history and the patient is not on current medications. His temperature is 37.7° C (100.0° F), pulse rate is 100/min, respiratory rate is 18/min, and blood pressure is 123/85 mm Hg. On physical examination, there is mild tenderness to palpation in the lower left quadrant of the abdomen with no rebound or guarding. Laboratory studies show anemia and thrombocytosis. Colonoscopy is performed, which confirms the diagnosis of ulcerative colitis (UC). What is the mechanism of action of the recommended first-line medication for the treatment of this patient’s condition?

Inhibition of leukotriene synthesis and lipoxygenase

Suppression of cellular and humoral immunity

Inhibition of enzyme phospholipase A2

A 27-year-old G0P0 female presents to her OB/GYN for a preconception visit to seek advice before becoming pregnant. A detailed history reveals no prior medical or surgical history, and she appears to be in good health currently. Her vaccination history is up-to-date. She denies tobacco or recreational drug use and admits to drinking 2 glasses of wine per week. She states that she is looking to start trying to become pregnant within the next month, hopefully by the end of January. Which of the following is NOT recommended as a next step for this patient's preconception care?

Administer measles, mumps, rubella (MMR) vaccination

Begin 400 mcg folic acid supplementation

Recommend inactivated influenza vaccination

A 31-year-old woman comes to the emergency department because of a 4-day history of fever and diarrhea. She has abdominal cramps and frequent bowel movements of small quantities of stool with blood and mucus. She has had multiple similar episodes over the past 8 months. Her temperature is 38.1°C (100.6°F), pulse is 75/min, and blood pressure is 130/80 mm Hg. Bowel sounds are normal. The abdomen is soft. There is tenderness to palpation in the left lower quadrant with guarding and no rebound. She receives appropriate treatment and recovers. Two weeks later, colonoscopy shows polypoid growths flanked by linear ulcers. A colonic biopsy specimen shows mucosal edema with distorted crypts and inflammatory cells in the lamina propria. Which of the following is the most appropriate recommendation for this patient?

Start annual colonoscopy starting in 8 years

Obtain barium follow-through radiography in 1 year

Obtain glutamate dehydrogenase antigen immunoassay now

Start annual magnetic resonance cholangiopancreatography screening in 10 years

A 23-year-old woman with no significant past medical history currently on oral contraceptive pills presents to the emergency department with pleuritic chest pain. She states that it started today. Yesterday she had a trip and returned via plane. Her temperature is 98°F (36.7°C), blood pressure is 117/66 mmHg, pulse is 105/min, respirations are 14/min, and oxygen saturation is 98% on room air. Physical exam reveals tachycardia, a normal S1 and S2, and clear breath sounds. The patient’s lower extremities are non-tender and symmetric. Chest pain is not reproducible with position changes or palpation but is worsened with deep breaths. Which of the following is the most appropriate next test for this patient?

Ultrasound of the lower extremities

A 67-year-old woman presents with right leg pain and swelling of 5 days’ duration. She has a history of hypertension for 15 years and had a recent hospitalization for pneumonia. She had been recuperating at home but on beginning to mobilize and walk, the right leg became painful and swollen. Her temperature is 37.1°C (98.7°F), the blood pressure is 130/80 mm Hg, and the pulse is 75/min. On physical examination, the right calf is 4 cm greater in circumference than the left when measured 10 cm below the tibial tuberosity. Dilated superficial veins are present on the right foot and the right leg is slightly redder than the left. There is some tenderness on palpation in the popliteal fossa behind the knee. Which of the following is the best initial step in the management of this patient’s condition?

Wells’ clinical probability tool

International normalized ratio (INR)

Computerized tomography (CT) with contrast

Activated partial thromboplastin time (aPTT)

A 17-year-old girl is brought to the physician by her parents for the evaluation of belly pain and a pruritic skin rash on her shoulders for the last 6 months. She describes feeling bloated after meals. Over the past 3 months, she has had multiple loose bowel movements per day. She appears thin. She is at the 20th percentile for height and 8th percentile for weight. Her temperature is 37°C (98.6°F), pulse is 90/min, respirations are 16/min, and blood pressure is 120/78 mm Hg. Examination shows conjunctival pallor and inflammation of the corners of the mouth. There are several tense, grouped subepidermal blisters on the shoulders bilaterally. The abdomen is soft, and there is diffuse tenderness to palpation with no guarding or rebound. Further evaluation of this patient is most likely to show which of the following findings?

IgA tissue transglutaminase antibodies

Inflammation of the terminal ileum

A 32-year-old man with Crohn disease is brought to the emergency department after he fainted at work. He says that he has been feeling increasingly fatigued and weak over the last several weeks though he has not previously had any episodes of syncope. On presentation he is found to be pale and agitated. A panel of lab tests is performed showing the following: Hemoglobin: 10.2 g/dL Hematocrit: 30.1% Leukocyte count: 9,900 cells/mm^3 with normal differential Platelet count: 290,000/mm^3 Mean corpuscular volume: 118 µm^3 Elevated homocysteine level Normal methylmalonic acid level Which of the following mechanisms explains how Crohn disease may have contributed to this patient's symptoms?

Release of acute phase proteins

IBD in pregnancy for USMLE Step 1: High-Yield Internal Medicine Lessons

Pre-Conception & Risks - The Baby Blueprint

Goal: Achieve and maintain remission for ≥3-6 months before conception. Disease activity, not medications, is the primary driver of adverse outcomes.
Maternal Risks (from active disease):
- ↑ Pre-eclampsia
- ↑ Venous Thromboembolism (VTE)
- ↑ C-section rates
Fetal Risks (from active disease):
- ↑ Preterm birth (<37 weeks)
- ↑ Low birth weight (<2500g)
- ↑ Small for Gestational Age (SGA)

⭐ Most IBD medications are safe in pregnancy. The key exception is Methotrexate, which is teratogenic and must be discontinued 3-6 months prior to conception in both men and women.

Maternal-fetal interface and IBD complications

Disease Activity & Fetal Outcomes - The Great Balancing Act

Primary Goal: Maintain remission ≥3 months pre-conception & throughout pregnancy.
Active inflammation is the principal driver of adverse outcomes, far outweighing the risks of most IBD medications.

⭐ The greatest risk for adverse fetal outcomes (e.g., preterm birth, low birth weight, SGA) stems from active maternal IBD, not from the majority of IBD medications used for maintenance.

Pharmacotherapy - Safe Harbor Meds

Maintaining remission is crucial; the risk of active IBD outweighs the risk of most medications. Generally, the pre-conception regimen should be continued, with exceptions noted below.

IBD Meds: Pregnancy & Breastfeeding Safety

Drug Class	Pregnancy Safety	Breastfeeding Safety
5-ASA Agents	Safe. ⚠️ Supplement with folic acid ($2 mg/day$) for sulfasalazine.	Safe.
Corticosteroids	Use for flares; lowest effective dose. Small ↑ risk of cleft palate (1st tri).	Safe.
Thiopurines	Safe. Benefits of disease control outweigh theoretical risks.	Safe.
Anti-TNFα Agents	Safe. Can be continued through pregnancy. Consider stopping at 24-26 wks.	Safe.

Delivery & Postpartum - The Final Push

Mode of Delivery:
- Vaginal delivery is preferred for most patients.
- C-section is indicated for active perianal disease (fistulas, abscesses) or a history of ileal pouch-anal anastomosis (IPAA) to protect sphincter function.
Postpartum Flare Risk:
- ↑ risk of flare, especially in the first 3 months postpartum.
- Risk is highest if IBD was active at conception or during pregnancy.
Breastfeeding & Meds:
- Encouraged; most IBD medications are compatible (e.g., 5-ASA, biologics).
- ⚠️ Contraindicated: Methotrexate, Tofacitinib.

⭐ Active perianal disease is a key indication for Cesarean section to prevent sphincter damage and worsening fistulas.

Delivery mode in IBD pregnancy

High‑Yield Points - ⚡ Biggest Takeaways

Disease activity at conception is the strongest predictor of flares during pregnancy.

Most IBD medications are safe, including 5-ASA, biologics (anti-TNF), and steroids.

Methotrexate is an absolute contraindication due to teratogenicity.

Sulfasalazine requires supplementation with high-dose folate.

Vaginal delivery is preferred unless there is active perianal disease.

Breastfeeding is safe with most IBD drugs; avoid methotrexate and cyclosporine.

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IBD in pregnancy