A clinician compares serum hCG patterns. Which single pattern is typical of a normal intrauterine pregnancy (versus an ectopic)?

Answer: D. hCG roughly doubles every 48 hours

Serum hCG patterns

Serial serum hCG helps distinguish a viable intrauterine pregnancy from an ectopic or failing pregnancy.

Patterns

• Normal intrauterine pregnancy: hCG roughly doubles every 48 hours.
• Ectopic pregnancy: the rise is often suboptimal (slower than doubling).
• Failing pregnancy: hCG falls.
• An abnormally high hCG may suggest a molar pregnancy.

Use

• Combined with transvaginal ultrasound, the hCG trend guides whether a pregnancy of unknown location is likely intrauterine, ectopic or failing.

So a normal intrauterine pregnancy roughly doubles its hCG every 48 hours.