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

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.