How Fast Should hCG Levels Rise in Early Pregnancy?
Have you been told that hCG levels have to double every two days in order to have a healthy pregnancy? What is the minimum increase needed? Let me make it easy for you to understand.
A viable baby is possible even if hCG levels don't double
Here is the quick summary. You can still have a healthy pregnancy and a viable live born baby even if your hCG levels do not double every two days. You can also have hCG levels that double or more than double every two days and NOT have a viable pregnancy. Let me explain.
What is hCG?
hCG is the hormone produced by some of the cells in an embryo.
After an embryo implants, the hCG is absorbed into the blood and can be measured with a blood test. As the cells in the embryo grow and divide, the hCG levels will increase.
When you see an IVF specialist, we will look at that hCG number and how it changes over time, in order to predict whether a pregnancy is viable or not.
For example, an hCG level that decreases over two days definitely indicates a non-viable pregnancy. A doubling of hCG levels means a 100% increase.
What is the minimum hCG increase needed?
But, if the hCG level doesn't have to double in two days, what is the slowest possible increase that still has a chance to be a viable pregnancy?
53 %. That's right! Your hCG level only has to go up by 53% over two days to indicate a viable pregnancy.
Confused? Let's take an example. If your first hCG level is 100, two days later you would want it to be at least 153. That is a 53% increase. That's not anywhere near to doubling.
But 99% of viable pregnancies are going to have an increase that is at least that. If we put it another way, only about 1% of viable pregnancies have an hCG level that rises less than 53% over two days.
Let me show you that you can do your first hCG blood test much earlier after an embryo transfer than you thought.
If your second hCG level only increased by 75% over two days, don't freak out! You are still in the expected range for a viable pregnancy. If it only increases by 40%... well, it's exceedingly unlikely that this will result in a baby.
Important exceptions to be aware of
There are a few important points to understand.
If you used hCG for your trigger injection before the egg retrieval and then did a fresh embryo transfer, there might still be hCG left in your body when you go to do your pregnancy test.
This could throw off the numbers.
Hopefully, your doctor only transferred one embryo into your uterus. But if you transferred multiple embryos, you could have a twin or a triplet pregnancy!!
This can really affect your hCG levels.
It becomes much harder to determine a viable pregnancy from a non-viable pregnancy in this case.
The examples I gave above work if you draw your hCG levels two days apart. Like Monday and Wednesday. If there was a longer time between the two blood draws, then use this chart to know the minimum increase for a viable pregnancy.
Chart for minimum hCG increase for different lengths of time