Do High Beta hCG Levels Mean You’re Having Twins? The short answer is no, the long answer is “it’s complicated”
If you’ve gone through fertility treatments, you’ve probably also experienced the beta test – the pregnancy blood test administered in the RE office approximately two weeks after ovulation/transfer to confirm whether or not you’re pregnant. The test detects the levels of the hormone hCG in your body, and is usually repeated after 2-3 days to check how quickly the hCG levels double. Here’s a great resource to learn more about the test.
My body didn’t typically wait for my scheduled beta test – a short luteal phase meant that my period usually came early and delivered the bad news in red scarlet letters. So when for once it was time for the beta test and I didn’t get my period yet, I was relieved, but I didn’t dare hope. When the nurse called in to say that my pregnancy blood test came back positive, I was in such a state of disbelief and excitement that I almost forgot to ask what my beta hCG level was. She said it was 600 and that it was a great number for 15 days post ovulation. I was happy.
Two days later, I came in for my second beta test, and this time my beta hCG levels were a whopping 1,600. “You’re very pregnant”, said the nurse, and I started asking myself: what could ‘very pregnant’ possibly mean? That’s when I started researching and found that my levels were high. Knowing that I was at a high risk of multiple pregnancy, I couldn’t help but wonder whether my high beta hCG levels meant that more than one embryo implanted in my womb. A quick Google search taught me that I’m not the only one asking this question.
Positive Beta Test Results Can Only Confirm That You’re Pregnant
Here’s the short answer to my question: beta hCG levels are only indicative of whether or not you’re pregnant, not how many embryos you are carrying. Beta levels of more than 5-10 at two weeks post ovulation mean that you’re pregnant, though low levels might indicate an ectopic pregnancy or miscarriage. Once the beta test confirmed you’re pregnant, though, it’s pretty much run its course. To know how many babies you’re having, you’ll need to wait until you get an ultrasound.
This is where we get into the gray area of probability, though. Yes, to know for sure whether you’re having one, two or more babies, you need an ultrasound. But what if you just wanted to get a sense of how likely you are to be having more than one? Clearly, when the nurse said I was very pregnant she suspected something was going on (spoiler: she was right, I had twins…).
So, I decided to geek out and try to get a better sense of the relationship between high beta hCG levels and twins or more. To do that, I used the fantastic resource called Betabase, a site that women have been updating with their beta test results and pregnancy information since 2004, and now has more than 100,000 pregnancies documented. A word of caution before I delve into the interesting results: the data in Betabase isn’t really representative of the overall population. For example, while twins are just 3.33% of all babies born in the US, about a third of the pregnancies in Betabase are of twins. I believe this is because women who get their beta test results at early stages (Betabase documents results from 10 days post ovulation) are almost always women who had fertility treatments and are therefore more likely to have multiples. I’m also assuming that women with high beta hCG levels were more likely to try to find out what their beta result means, find the site and log their information, which means high values are probably overrepresented. In other words, Betabase probably overstates the occurrence of high beta hCG levels and of multiple gestations. This means that you should take my findings with a grain of salt, but I think it’s safe to say that they are, at the very least, directionally accurate. And here’s the biggest takeaway:
Higher Beta hCG Levels are Correlated with Higher Occurrence of Twins and High-Order Multiples
I looked at the data two ways. First, I analyzed the median beta hCG score for each type of pregnancy (singleton, twins, high-order multiple), day by day. This means that half the pregnancies in the category had higher beta hCG levels and half had lower beta hCG levels.
As you can see in the graph, the median beta level was always higher the more babies a woman carried. However, medians don’t really tell the whole story, because each individual test result can fall above or below that mid-point. There was, in fact, quite a bit of overlap between the different categories. For example, on 14 days post ovulation, the most popular time for women undergoing infertility treatments to take the beta hCG test for the first time, hCG levels for singletons ranged from 9 to 1,666, hCG levels for twins ranged from 17 to 8,270, and hCG levels for high-order multiples ranged between 54 and 971. So if, for example, you have a beta result of 400, your result falls into the range of each type of pregnancy. You have no way of knowing whether you have a high result for a singleton or a more average result for twins, so you’re left with as many questions as you’ve had when you started.
That’s why I decided to dig deeper into the Betabase data to try and understand what the likelihood is of having each type of pregnancy based on one’s beta test results. Once again, I picked 14 DPO (or 9dp5dt / 11dp3dt for those having IVF) as my reference point, because I figured this would be most helpful to women in the infertility community. What I found was that the higher women’s beta levels were, the more likely they were to have more than one baby. Of the 1,535 pregnancies with 14 DPO beta numbers in Betabase, 59% were of singletons, 34% were of twins, and 7% were of triplets or more. However, when slicing the data by beta hCG levels, the distribution was quite different. For example, 93% of women with beta levels lower than 80 had singletons, compared to only 25% of women with beta levels between 300 and 600. As the graph shows, the occurrence of twins and triplets kept increasing as the beta hCG levels climbed up.
My takeaway from all this is simple: how you want to treat your hCG beta test results is all about how comfortable you feel with uncertainty. If you like black-and-white answers, know that your beta numbers are not indicative of how many babies you’re carrying. Only an ultrasound can give you a definitive answer. However, if you feel comfortable spending the few weeks between the beta test and the ultrasound in the gray kingdom of uncertainty, you can use the table on the right as a very rough rule of thumb to help you understand whether your beta hCG levels falls within the “typical” range for singleton or twins (with “typical” being the range in which approximately 70-85% of test results are concentrated according to Betabase). There’s a lot of overlap between the two categories, so you could very well find yourself in both, but at least in my case, understanding these numbers helped prepare me for finding out I had twins when I finally got my ultrasound at eight weeks pregnant. Not that anything can really prepare you for that shock, but you know what I mean…
What were your beta hCG levels and what did you end up having? Did you fall within the “typical” range for your type of gestation?