How Does a Human Chorionic Gonadotropin (hCG) Test Work to Confirm That I’m Pregnant?

From the moment of conception, your body starts going through changes to support the growth of the embryo and fetus. Many changes during pregnancy are driven by hormones like human chorionic gonadotropin (hCG), a hormone that’s normally undetectable. 

Pregnancy tests measure hCG levels to confirm pregnancy.

At CARE Fertility in Bedford and Fort Worth, Texas, our reproductive endocrinology and infertility specialists love nothing more than a positive pregnancy test, and the hCG test is the test we use to check for pregnancy.

Here, we explain hCG and how the pregnancy test works to confirm that you’re pregnant.

About hCG

Human chorionic gonadotropin (hCG) is a hormone that’s present in the body but at undetectable levels; it’s only produced during pregnancy. When sperm fertilizes an egg in the fallopian tube, it creates an embryo. After formation, the embryo’s goal is to get to the uterus and implant itself into the wall of the uterus.

Embryo implantation kick-starts the formation of the placenta, the tissue that connects the mother and the fetus, providing oxygen and nutrients for a growing baby. 

The placenta produces and releases hCG. The hormone signals the body to increase the production of estrogen and progesterone and tells the body to stop ovulation and menstruation and to thicken the lining of the uterus.

You need all three hormones in balance to support pregnancy.

Pregnancy tests

Urine and blood pregnancy tests confirm pregnancy by measuring hCG levels. The placenta makes hCG right away, and levels double several times during the first few weeks of pregnancy. 

Some at-home urine tests detect hCG within 10 days after conception. However, not all at-home pregnancy tests are this sensitive — and you can get negative results when checking too early. We recommend that you wait until you miss your period before taking an at-home pregnancy test.

Blood pregnancy tests are more sensitive than urine tests and can detect hCG within 7-10 days of conception. We do blood tests to check hCG levels and confirm pregnancy for our patients undergoing infertility treatments like in vitro fertilization (IVF).

Accuracy of hCG results

If you’ve been struggling with infertility or have a history of multiple miscarriages, you may worry about the accuracy of hCG tests for confirming pregnancy. However, these tests are very exact when done correctly.

Most false results occur because of inaccurate testing, such as testing negative when you do a urine pregnancy test prematurely. Too much or too little urine may also result in a false negative test. 

Blood hCG tests can detect the slightest change in hCG levels and accurately confirm pregnancy within days of conception. But you can have false positive results from a blood hCG test if you had an early miscarriage. 

Once we confirm pregnancy with the hCG test, we perform an ultrasound to evaluate the placenta and embryo and estimate the due date.

The hCG test is the gold standard for confirming pregnancy. Blood tests are more sensitive to changing hormone levels and can confirm pregnancy within the first 10 days of conception. 

At CARE Fertility, we do all diagnostic testing on site using a state-of-the-art system that gets fast and accurate results. Learn more about our infertility tests and treatments by calling the office or requesting an appointment online with one of our specialists.