Human chorionic gonadotropin (hCG) is a hormone created by the trophoblast tissue, tissue that is found in early embryos that will eventually be part of the placenta during pregnancy. It’s frequently measured via a blood test, to detect pregnancy after an embryo transfer or IUI, and in early pregnancy.
What do hCG Levels mean?
When hCG is detected in the body, it indicates that implantation has taken place. When an embryo implants and hCG levels start to rise, it triggers the body to make important pregnancy hormones such as progesterone and oestrogen.
How long after implantation does hCG rise?
Once the embryo has implanted in the uterus, the hCG hormone starts to rise.
It usually takes about 6-12 days for the hCG levels to become detectable in a blood or urine test, which is why we have what’s known as the “two-week wait” post-embryo transfer.
Once detectable, we expect the hCG levels to approximately double every two days. hCG levels can vary dramatically from person to person and pregnancy to pregnancy, so it is important not to compare these levels to other people.
What is the beta blood test?
A blood test for hCG, sometimes known as a “beta blood test” or a “pregnancy blood test”, is usually taken to measure the levels of hCG in the body
A total of three beta blood tests are usually recommended. The first will be taken around the day of you received a positive at home pregnancy test. The second and third will then follow every 48 hours after. With each blood test, we would expect the hCG levels to have approximately doubled, if the pregnancy is progressing normally.
What happens after the beta hCG test?
Assuming all three tests are as we would expect, you will be offered a transvaginal ultrasound at around roughly 5 weeks after ovulation or 4 weeks after embryo transfer) to confirm that the gestation sac is in the correct location, that the pregnancy is the correct size and that a heartbeat is present.
This ultrasound is much more predictive of pregnancy outcomes than hCG levels. So, if your first beta is low, don’t panic!
hCG Levels by Week
We often get asked what are normal hCG results throughout pregnancy?
hCG levels vary significantly from person to person. It’s not so much the level itself that is important, more the rise we see between each blood test.
In the first few weeks, the levels will increase rapidly, provided the pregnancy is developing as expected. Eventually, the levels will peak and begin to plateau usually around 8 weeks of pregnancy.
What if my hCG level is lower than expected?
We understand it can be an extremely anxious time once you do get a positive pregnancy test, but it’s important to try not to obsess too much over the hCG numbers.
The beta hCG level is not an absolute indicator of the success of an IVF embryo transfer. A low beta hCG level can be worrying, but there are many normal, healthy pregnancies that start out with a low beta hCG.
An ultrasound at seven weeks is a much more predictive of pregnancy outcomes than the hCG levels.
If you have concerns about your beta hCG numbers, always talk to your doctor or nursing team. Don’t be afraid to ask them what they think is going on and what your chances are of success given the information at hand.
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