The B-hCG curve in maternal serum in a normal pregnancy peaks at: A. 6 weeks of pregnancy. B. 8 weeks of pregnancy. C. 10 weeks of pregnancy. D. 14 weeks of pregnancy. E. 18 weeks of pregnancy.
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The answer is C. 10 weeks of pregnancy.
β-hCG peaks at approximately 10 weeks of gestation, then gradually declines to a plateau for the remainder of pregnancy.
Key supporting data from the textbooks:
- Berek & Novak's Gynecology: "β-hCG levels peak at approximately 10 weeks gestation."
- Henry's Clinical Diagnosis and Management by Laboratory Methods: "Serum hCG increases dramatically during the first trimester, reaching a peak at about 10–16 weeks' gestation."
- Creasy & Resnik's Maternal-Fetal Medicine: "hCG has peak concentration at between 8 and 12 weeks and then declines."
- Rosen's Emergency Medicine: "β-hCG levels peak at the 7- to 10-week mark."
The most commonly cited and exam-standard answer is 10 weeks, which represents the peak of the β-hCG curve in a normal singleton intrauterine pregnancy. After this peak, levels decline and plateau around 18–20 weeks.
Why this matters clinically: The β-hCG peak around 10 weeks correlates with peak placental trophoblastic activity. This is also the window associated with hyperemesis gravidarum (nausea/vomiting driven by high hCG levels) and gestational thyrotoxicosis (hCG cross-reacts with TSH receptors).
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