Arguably, the most nerve-wracking part of the IVF process is the fabled “Two Week Wait.” For those who are new to IVF, this is the period between the embryo transfer and the time that the woman receives the results of her first pregnancy test. The type of pregnancy test that is administered following IVF is a blood pregnancy test that is much more sensitive than an over-the-counter urine test, though both types of test measure the concentration of a hormone called Human Chorionic Gonadotropin or hCG. The blood test is commonly referred to as a beta hCG test, or simply a “beta.” Two or more beta hCG tests are performed on IVF patients, usually two days apart. The reason that multiple betas are done is that we are looking at the rate of change (ideally an increase) in the hCG level.
After the extensive time, expense, effort, pain, worry and emotion dedicated to preparing for and undergoing an IVF treatment cycle, all hopes seem to hinge on that number that the nurse coordinator relays to a patient – usually over the phone. This is the moment when a patient finds out if her IVF cycle “worked” (at least, that is the perception). In technical terms, this “beta” number represents the number of units of hCG per ml in the blood. Because it measures concentration of hCG in the blood, it’s not simply a “positive” or “negative” test, but a matter of degrees in many cases. Though a level of zero is a fairly reliable indicator that there is no developing pregnancy, there is not a definitive threshold number that reliably indicates a viable pregnancy.
When the phone finally rings on that blessed/dreaded day, patients may be subjected to more suspense and worry if the number isn’t what they consider “good” based on what another patient, friend, relative or stranger has told them. So…what is a “good” beta number in IVF? That’s a “good” question. And the short answer is not very reassuring. As with so many aspects of IVF, the answer is “It depends.”
There is a range that many (not all) viable IVF pregnancies fall into. The fact is, I have seen beta numbers as low as 4 that went on to result in a healthy baby and I have seen first beta numbers over 100 that ended in a chemical pregnancy. It is important to understand that the much more reliable and predictive indicator of a viable pregnancy is the rate at which the Beta hCG number increases. We like to see a beta number roughly double every 48 hours (though it may take up to 72 hours to double). For example, if the first beta hCG number is 24, the second beta number should be in the neighborhood of 40-60. Even with a high first beta number, a failure to double in 48-72 hours is a possible indication that the pregnancy is beginning to arrest. Likewise, even an extremely low first beta number isn’t cause for panic or pessimism if it increases at an acceptable rate.
With that said, there are a number of circumstances in which beta numbers don’t follow this pattern, even in a viable pregnancy. For example, a twin or other multiple gestation may show a high initial beta number as two fetuses begin to form and grow. If one fetus arrests, this can cause the beta number to increase at a slower rate, throwing the prospective mother into a panic. In a case like this, we may do a third and even a fourth beta hCG to allow the numbers to stabilize and resume a more predictable pattern. In many cases of multiple gestations that are progressing well, the beta number may increase at a more rapid rate, sometimes quadrupling in 2 days.
With so much uncertainty and variability in beta numbers, how can we tell if a number is “good”? The answer is that a beta number that is doubling in the appropriate time frame is much more likely to be a viable pregnancy than one that is not, even though there are circumstances where it falls outside of these parameters.
At the risk of being held to these numbers, here are some rough beta guidelines. I post these mostly to show how variable the numbers can be, even in viable pregnancies:
• 2 weeks post transfer: 5 – 50 mIU/ml
• 3 weeks post transfer: 5 – 426 mIU/ml
• 4 weeks post transfer: 18 – 7,340 mIU/ml
• 5 weeks post transfer: 1,080 – 56,500 mIU/ml
• 6-7 weeks post transfer: 7, 650 – 229,000 mIU/ml
(Source: American Pregnancy Association)
At approximately 6-7 weeks past transfer, an ultrasound confirmation of pregnancy can be made and the miraculous and magical sound of a heartbeat can be heard in viable pregnancies…introducing the next stage of worry for expectant couples.
To summarize, there is a wide range of “normal” when it comes to beta hCG pregnancy test results. The key factor that we look at is doubling time of the beta number. Above all, know that we welcome and encourage your calls with any questions or concerns you might have during this or any other stage of your care.