Review Question - QID 214631

A 27-year-old G2P1001 woman at 34 weeks gestation arrives to the emergency room with nausea, vomiting, and worsening right upper quadrant pain that began 2 hours after a pizza dinner last night. The pain is severe and constant, radiating to the right shoulder. A review of systems is positive for fever and chills. The patient does not endorse hematemesis or shortness of breath. The patient's temperature is 101.5°F (38.6°C), blood pressure is 110/70 mmHg, pulse is 104/min, respirations are 20/min, and oxygen saturation is 98% on room air. BMI is 30 kg/m^2. Fetal heart rate tracing demonstrates a baseline rate of 140/min, moderate variability, and no decelerations. Abdominal examination demonstrates right upper quadrant tenderness as well as voluntary and involuntary guarding. When the right upper quadrant is palpated, the patient stops inspiring. The cardiac exam demonstrates a flow murmur. The pulmonary exam is unremarkable. Laboratory results indicate the following:

Hemoglobin: 11.5 g/dL
Leukocyte count: 17,500/mm^3
Bands: 15%
Platelet count: 225,000/mm^3
Total bilirubin: 3 mg/dL
Indirect bilirubin: 2.3 mg/dL
Lipase: 72 U/L

What physiologic changes of pregnancy most likely contributed to this patient's condition?