Defining the rise of serum HCG in viable pregnancies achieved through use of IVF

BACKGROUND: We aimed to characterize the rate of HCG rise associated with viable IVF pregnancies, and to evaluate the association between HCG rise and potentially influential factors. METHODS: We performed a retrospective cohort analysis of all viable pregnancies achieved through IVF at two centres between January 1999 and March 2004. RESULTS: Of the 455 pregnancies resulting in live births, 391 met inclusion criteria and contributed a total of 1052 HCG values. Using random effects models, the best pattern to describe the rise of log HCG was quadratic with the rate of increase slowing at 24 days post-oocyte retrieval. Limiting the analysis to measurements below the discriminatory zone, the linear model adequately characterized the profile. The average slope was 0.403, yielding a predicted increase of 1.50 (50% increase) in 1 day and 2.24 (124%) in 2 days. In the final model, absolute HCG values, but not rate of rise, were significantly higher for twins and triplets and significantly lower for patients with BMI >30 kg/m 2 . CONCLUSIONS: The HCG profile of viable pregnancies conceived with IVF is quadratic with an