Predicting the Decline in Human Chorionic Gonadotropin in a Resolving Pregnancy of Unknown Location

Butts, Samantha F. MD, MSCE; Guo, Wensheng PhD; Cary, Mark S. PhD; Chung, Karine MD, MSCE; Takacs, Peter MD, PhD; Sammel, Mary D. ScD; Barnhart, Kurt T. MD, MSCE

doi: 10.1097/AOG.0b013e31829c6ed6
Original Research

OBJECTIVES: To characterize the curve derived from serial human chorionic gonadotropin (hCG) values in women with spontaneous resolution of pregnancy of unknown location and to assess factors that modify the decline.

METHODS: Data from three sites were extracted from a clinical database of women with a symptomatic pregnancy of unknown location that required follow-up with serial hCG levels. A nonlinear mixed-effects regression model was used to generate hCG elimination curves.

RESULTS: Four hundred forty-three women presenting with a pregnancy of unknown location that resolved without intervention were studied between September 2007 and May 2009. Women older than 35 years had a slower hCG decline (P=.001) and those with pain had a steeper decline (P=.006), but these changes did not alter the curve in a clinically meaningful way. The decline in hCG is faster for those with a higher level at presentation. The average decline of hCG in women with spontaneous resolution is slower than previously reported. However, the minimal decline in hCG for women with spontaneous resolution of a pregnancy of unknown location ranged from 35% to 50% at 2 days of follow-up and from 66% to 87% at 7 days, which is more rapid than previously reported.

CONCLUSION: In a diverse population, using updated statistical methods, it was observed that the minimal decline in hCG for women with spontaneous resolution is more rapid than previously reported. A decline slower than these thresholds may indicate the presence of retained trophoblastic tissue or ectopic pregnancy.

LEVEL OF EVIDENCE: III

In a diverse population using updated methods, the minimum human chorionic gonadotropin decline in a resolved pregnancy of unknown location is more rapid than previously published.

Department of Obstetrics and Gynecology and the Center for Clinical Epidemiology and Biostatistics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania; the University of Southern California, Keck School of Medicine, Department of Obstetrics and Gynecology, Los Angeles, California; and the Department of Obstetrics and Gynecology, University of Miami School of Medicine, Miami, Florida.

Corresponding author: Kurt Barnhart, MD, MSCE, 3701 Market Street, Suite 810, Philadelphia, PA 19104; e-mail: kbarnhart@obgyn.upenn.edu.

Supported by grants from NICHD R01-HD036455 (K.T.B., M.D.S.), NICHD K24HD060687 (K.T.B.), NICHD U54-HD-068157 (S.F.B.), and NIEHS P30 ES013508-07 (S.F.B.).

Financial Disclosure Dr. Sammel is a paid consultant for Swiss Precision Diagnostics. The other authors did not report any potential conflicts of interest.

Presented as a poster at the 67th annual meeting of the American Society for Reproductive Medicine, October 16–19, 2011, Orlando, Florida.

© 2013 by The American College of Obstetricians and Gynecologists.