The hCG ratio can predict the ultimate viability of the intrauterine pregnancies of uncertain viability in the pregnancy of unknown location population

Abstract

Background: To determine whether hCG ratio at 48 h can predict ultimate viability of intrauterine pregnancies of uncertain viability (IPUVs) in the pregnancy of unknown location (PUL) population.

Methods: Prospective observational study from June 2001 to October 2004. All women classified with PUL had serum hCG levels measured at 0 and 48 h to calculate hCG ratio (hCG 48/hCG 0 h). All women were followed up until final diagnosis: failing PUL, viable and non-viable intrauterine pregnancy (IUP), ectopic pregnancy. Those PULs found to have an IPUV at follow-up transvaginal ultrasound scan (TVS) were included in final analysis.

Results: During the study period, 12,572 consecutive first trimester women were scanned. One thousand and three (8%) women were classified PULs. Three hundred and seventy-nine (37.8%) PULs were confirmed IPUVs at follow-up scan. Complete data from 334 IPUVs were analyzed: 82.6% (276/334) viable IUPs and 17.4% (58/334) non-viable IUPs. Median hCG ratio was greater in viable IUPs [2.32, inter-quartile range (IQR) 1.16-4.77] compared with non-viable IUPs 1.83 (IQR 0.97-4.60). Sensitivity, specificity, positive and negative predictive value, positive and negative likelihood ratios of an hCG ratio >2.00 for the prediction of a viable IUP are 77.2%, 95.8%, 86.6%, 90.9%, 15.5, 0.24, respectively. In our population, an hCG ratio >2.00 increases the odds for a viable IUP from 0.42 to 6.46 post-test.

Conclusions: The hCG ratio is significantly higher in those IPUVs which become viable IUPs compared with non-viable IUPs. New cut-offs for the hCG ratio need to be evaluated for the prediction of viability in the IPUV group of PULs.