IS EARLY HCG PREDICTIVE OF PREGNANCY AFTER ESET IN BOTH FRESH AND FET CYCLES?

Abstract

Most ART programs perform β-hCG measurement 9-12 days after embryo transfer(ET) to detect a pregnancy. A prior study using hyperglycosylated hCG in a small sample size showed that a single measurement 6 days after ET had 100% sensitivity and specificity in identifying biochemical and ongoing pregnancies. We sought to determine whether routine serum β-hCG measurement at 5-6 days after ET is predictive of ART outcome. This is important in patient counseling if we can stop P supplementation early in cases of negative tests, especially if taking painful IM P supplementation. Prospective single center. A total of 241 patients undergoing eSET (elective single embryo transfer) had their “early” serum β-hCG measured 5-6 days after ET, and the “official” serum β-hCG was done 9-10 days after ET. There were 91 fresh ET and 150 FET cycles. A test was positive if the β-hCG measurement was ≥ 3 IU/L. All tests were performed at a commercial laboratory with offices around the US (LabCorp). In the 91 fresh ET cases observed, 65 had positive and 26 had negative “early”β-hCG tests measured 5-6 days post ET. Of the 65 positive β-hCG tests, 10 (15.4%) were biochemical, 9 (13.8%) were pregnancy losses (SAB), and 46 (70.8%) were live births. Of the 26 negative tests, 24 (92.3%) were negative on days 9-10 and 2 (7.6%) were positive on days 9-10. Both positive results on day 9-10 ended with biochemical losses. In the 150 FETs observed, 81 had positive and 69 had negative “early” β-hCG. Of the 81 positive, 19 (23.5%) were biochemical pregnancies, 7 (8.6%) had SAB, and 55 (67.9%) were ongoing/live births. Of the 69 negative β-hCG tests measured 5-6 days post FET, 4 (5.7%) were then positive on day 9-10, 3 resulting in biochemical pregnancies and one live birth. The mean “early” β-hCG levels in the IVF group was 27.03 IU/L which was significantly higher than in the FET 14.09 IU/L (P<0.001). There were significant differences in early β-hCG results between ongoing/delivered and biochemical pregnancies in both fresh and FET groups (P<0.001), but not between ongoing/LB and SAB. However, by first β-hCG level on days 9-10 there were no differences in the mean β-hCG between the 2 groups (P=0.04). ROC for fresh ET showed a cut off value of 7 IU/L. The test can detect with 90% sensitivity a 96% specificity with 3.8% false positive (AUC=0.972). For FET it showed a cut off value of 3.7 IU/L. The test can detect with 89% sensitivity a specificity of 94% with 5.7% false positive (AUC=0.964) (Figure 1). Early serum β-hCG measured 5-6 days after ET in eSET cycles is very predictive of successful pregnancies. A negative test 5-6 days after ET is associated with a negative 9-10 day β-hCG test in both fresh and FET cycles. In the fresh group, an early negative β-hCG was 100% predictive of no live births, but in the FET group an early negative in the FET group led to a single live birth (99.33% predictive of no live births). FET cycles were associated with lower early β-hCG levels than fresh transfers but became similar to fresh cycles on the first day of actual pregnancy test. This information is of potential benefit in counseling women undergoing ART.