Gallbladder disease (cholelithiasis or cholecystitis): This is a common cause of right upper quadrant (RUQ) pain, especially in pregnant women due to increased bile stasis and cholesterol stone formation. The symptoms can be exacerbated by the enlarged uterus compressing the gallbladder.

Peptic ulcer disease: Pregnancy can increase the risk of peptic ulcers due to increased gastric acid production and decreased motility. Severe abdominal pain, especially in the RUQ, can be a presenting symptom.
Pyelonephritis: Although more commonly associated with flank pain, pyelonephritis can cause severe abdominal pain, including in the RUQ, especially if the right kidney is involved.
Hepatitis: Viral or drug-induced hepatitis can cause RUQ pain and is a consideration in pregnant women, especially if there are risk factors for viral hepatitis.

Preeclampsia with HELLP syndrome: Although typically associated with hypertension and proteinuria, preeclampsia can cause severe abdominal pain, including in the RUQ, due to liver capsule distension in HELLP syndrome.
Appendicitis: While the appendix may be displaced upward during pregnancy, making the diagnosis more challenging, appendicitis remains a critical diagnosis to consider due to its potential for severe complications if not promptly treated.
Hepatic rupture or infarct: Rare but potentially life-threatening conditions that can cause severe RUQ pain and are associated with preeclampsia or other vascular issues.

Budd-Chiari syndrome: A rare condition caused by hepatic vein thrombosis, leading to liver congestion and potentially severe RUQ pain.
Adrenal hemorrhage: Although rare, it can cause severe abdominal pain, including in the RUQ, and is associated with significant morbidity if not promptly diagnosed and treated.
Intrahepatic cholestasis of pregnancy (ICP): While typically causing pruritus, ICP can also lead to RUQ pain due to bile duct obstruction and liver dysfunction.