A 26-year-old woman at 34 weeks of gestation has routine labs showing alkaline phosphatase 280 U/L (normal 40 to 120). GGT, ALT, AST, bilirubin, and bile acids are all normal. She is asymptomatic. What is the most likely explanation?

• A Intrahepatic cholestasis of pregnancy
• B Physiological placental alkaline phosphatase release ✓
• C Occult biliary obstruction
• D Vitamin D deficiency with secondary hyperparathyroidism

Explanation

The placenta produces its own alkaline phosphatase isoenzyme from around the second trimester, and serum levels can reach two to four times normal near term; this is physiological. Normal bile acids, normal GGT, and absence of pruritus exclude intrahepatic cholestasis of pregnancy, the most tempting distractor, which characteristically shows raised maternal serum bile salts and pruritus. Vitamin D deficiency would elevate bone alkaline phosphatase, not produce this isolated benign picture.

Reference: Williams Obstetrics, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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