Blood Tests to Determine Pregnancy

Pregnancy blood tests, also known as pregnancy serum tests, are created to measure the amount of human chorionic gonadotropin, or hCG, in the bloodstream to determine if a woman is pregnant. Within 10 days of fertilization, this hormone will be evident in the bloodstream, as the placenta will begin releasing it almost immediately after conception. There are two primary pregnancy blood tests. These include the quantitative blood test, which measures the exact concentration of hCG in the blood, and the qualitative test, which will simply indicate if hCG is present.

At What Point Can a Blood Test Determine Whether or Not a Woman is Pregnant?

Blood tests are able to detect pregnancy about 7 to 12 days after conception, making them a better option than most at home pregnancy tests. Unlike home pregnancy tests, they can also determine the level of hCG in your blood. This is particularly useful information for your doctor because it can help reveal information about specific problems commonly experienced during pregnancy. If you ever suspect that you are pregnant because you’re experiencing tenderness of the breasts, pelvic pain, irregular spotting, delayed menstruation, or vomiting, a blood test must be performed to determine whether or not you’re pregnant.

How Accurate is a Blood Test Compared to a Urine Test at Determining Pregnancy?

Due to recent research, it is now believed that blood tests are more accurate than urine tests when it comes to accurately determining pregnancy. According to research from the Scientific Assembly of the American College of Emergency Physicians, about six percent of pregnancies that are reported negative from urine testing come back positive with blood testing. The researchers involved in this study did not expect this result, as they believed that blood and urine pregnancy tests had comparable accuracy.

Additionally, researchers at Henry Ford Hospital examined 662 women who received both urine and blood testing for hCG. Out of the 102 negative results received, six women who tested negative with a urine test were then shown to be pregnant through blood testing. Five of the six women in this group had hCG levels ranging from 11 to 97 mU/ml, a level that is expected during the first month of pregnancy.



While researchers are always wary to claim that false negative numbers such as those reflected in the study are expected, blood pregnancy tests are now used for all women at Henry Ford Hospital who are less than four weeks past their typical menstrual period. As a result, it can be concluded that blood tests are in fact more accurate than urine tests at detecting pregnancy.

What is Meant by the Pregnancy Blood Test Results?

Healthy pregnancies reflect normal hCG levels throughout the entire pregnancy. During the first trimester, it is expected that human chorionic gonadotropin (hCG) levels increase to then decrease throughout the remainder of the pregnancy. Testing is regularly done throughout the first trimester to determine whether or not hCG levels are rising as expected because if they don’t, something might be wrong. Once a child is born, a miscarriage occurs, or an abortion is performed, hCG levels are expected to be at zero once again.

Are Blood Pregnancy Tests Reliable?

The reliability of the results are highly dependent on the lab, methodology, and technique being used for the blood tests. In general, blood tests are more accurate than home pregnancy tests, which have an accuracy level of about 97 percent. However, it’s important to note that blood tests might be more accurate, but not always more sensitive.