Value of single and paired serum human chorionic gonadotropin measurements in predicting outcome of in vitro fertilisation pregnancy

Objectives: To assess whether paired human chorionic gonadotropin (hCG) measurements in early pregnancy are more effective than a single measurement, in predicting the outcome for an in vitro fertilisation pregnancy. Design: Retrospective analysis. Setting: Westmead Fertility Centre, Westmead Hospital, Sydney, Australia. Materials and methods: Serial hCG measurements in 143 patients at Westmead Fertility Centre, from August 1997 to April 2000, were studied retrospectively. The predictive value of single hCG measurements relative to the published assay reference ranges were evaluated. The predictive value of serial hCG levels in predicting pregnancy outcome was assessed separately. Normal daily rate of rise (ROR) of hCG was defined as the mean ROR for ongoing pregnancies +/- 1 SD. Abnormal daily ROR was defined as a daily increase in hCG less than the mean ROR for ongoing pregnancies -1 SD. Main outcome measures: Viability of the pregnancy at 20 weeks' gestation. Results: An initial hCG measurement below the 5th centile reference limit for gestation has 85% (confidence interval (CI) 75-92%) positive predictive value for non-viability, with a sensitivity of 40% (CI 33-48). Serial testing of borderline samples for ROR did not improve positive predictive value (70%: Cl 50-86%) or sensitivity (30%: Cl 20-43%) in identifying non-ongoing pregnancies. Conclusions: In assisted reproductive technologies pregnancies, comparison of a single hCG value with appropriate reference ranges enables approximately 40% of non-viable pregnancies to be identified with a high positive predictive value. Repeated measurements did not contribute further to the predictive value.