You’ve seen a fertility specialist, started IVF, and gotten through the first embryo transfer. You’ve spent a long time waiting for good news. And finally you get it! The results of your pregnancy test, which measures hCG level, are positive. Congratulations!
Almost before you can celebrate, however, you start wondering, “Is my hCG level good?” Is the pregnancy going to progress normally?
What Is hCG?
First some basics. Human chorionic gonadotropin (hCG) is a hormone that is released by the human embryo after conception. It is used to diagnose pregnancy and a result greater than 5 mIU/mL is generally considered positive. The hCG level has to rise appropriately (it doubles every 3 days or so in early pregnancy) till it reaches around 1500 mIU/mL. At that point, a pregnancy should be visualized in the uterine cavity using a transvaginal ultrasound.
hCG levels are higher in multifetal pregnancies than singleton. In patients that are having biochemical pregnancies, miscarriages or tubal pregnancies, the levels will not rise appropriately. It is therefore important that patients keep their follow-up monitoring visits and continue their medications until they are instructed not to do so by their physician.
What Should My hCG Level Be?
So, what is a good first hCG level after embryo transfer? This very question was addressed by a group from Finland (Poikkeus P. et al, Serum hCG 12 days after embryo transfer in predicting pregnancy outcome. Hum Reprod 2002; 17:1901-05). They analyzed a total of 774 embryo transfers from 1994 – 1999. Embryo transfer was carried out 2 days after retrieval and the first pregnancy test was scheduled 12 days later (14 days after retrieval). Here is what they found:
The median hCG concentration was 126 mIU/mL in viable pregnancies and 31 mIU/mL in non-viable pregnancies (four times higher; P < 0.0001). The median hCG level in twin pregnancies was almost double that in singleton pregnancies (201 mIU/mL vs. 115 mIU/mL). With detailed statistical analysis (ROC curve) they concluded that an hCG level of 76 mIU/mL was a suitable cut-off point for predicting viable pregnancy with 80% sensitivity and 82% specificity. The positive predictive value for a viable pregnancy at this level was 87% and the negative predictive value was 74%. All biochemical pregnancies were found at hCG levels < 100 mIU/mL.
What if My hCG Levels Aren’t Over 100?
It is important NOT to take these numbers literally. There are many variables that can affect hCG values, including the assay that is being used. These numbers are specific to the assay the researchers used (solid phase, two-site fluroimmunometric assay calibrated against the WHO Third International Standard of hCG for immunoassay). hCG levels are different for day 3 vs. day 5 transfers.