Blood tests and home pregnancy tests are the two most used methods for detecting pregnancy.
When you miss a period or undergo fertility treatment, you may want to find out if you are pregnant as soon as you can. Most women start with the home pregnancy test and then visit their doctors if they get positive results. However, there are times when it may be better to wait for the blood analysis.
If you think that you may be pregnant, you may have a lot to consider, including the effectiveness of these different tests. You may want to know more about their accuracy and costs or how long it takes to get your results.
What Is a Blood Test for Detecting Pregnancies?
Blood tests are taken at a doctor’s office or fertility clinic to search for the presence of the human chorionic gonadotropin hormone (hCG). This hormone is called the pregnancy hormone.
After fertilization, your body begins producing increased levels of this pregnancy hormone. The hormone can be detected in your bloodstream and urine.
With blood tests, doctors either use a quantitative or qualitative test. Both tests detect the pregnancy hormone. However, the quantitative blood test can detect lower levels of the pregnancy hormone. With the quantitative blood test, you can detect pregnancies earlier and more accurately.
Blood Tests Can Detect Pregnancy Hormones Early
The ovulation window is short. There are a couple of days each month that you can get pregnant. If you get pregnant, your body should begin producing the pregnancy hormone.
Blood tests may detect the pregnancy hormone as early as eight days after you ovulated. This should be about one week ahead of your upcoming period.
Home pregnancy tests look for the pregnancy hormone in your urine. However, it is harder to detect in your urine compared to your blood. You need to wait longer for higher levels of the hormone to appear. In most cases, you need to wait a few days after your missed period.
While the exact levels of the hormone vary, most women can get results at least two weeks earlier with a blood test compared to a home pregnancy test.
Blood Tests Provide the Most Accurate Results
Blood tests are the most accurate test for detecting pregnancy. They are accurate over 99% of the time. As mentioned, it is easier to detect the pregnancy hormone in your blood compared to your urine.
Home pregnancy tests are less accurate. While the top pregnancy tests claim to offer 98% accuracy, the typical test is only 94% accurate. There is also a greater risk of user error when taking home pregnancy tests.
The best home pregnancy tests can only detect the pregnancy hormone about one week after your missed period. If you take the test too early, you are more likely to get a false negative result.
You May Need to Wait Two to Three Days for Results
The one drawback to the blood test is that you may need to wait two to three days for results. After your blood is taken, your doctor or fertility specialist likely sends it to a laboratory for analysis.
Some labs can complete the analysis in a few hours. However, the average wait time is two to three days. The exact amount of time depends on the lab. If they are busy or understaffed, the results may take longer.
False Positive and False Negative Results Are Possible
While blood tests are accurate, false positive and negative results are possible. For example, ectopic pregnancies may result in false negative results when testing too early.
With an ectopic pregnancy, the egg is attached to the fallopian tube instead of attaching to the uterus. In some cases, your body may continue producing pregnancy hormones, which may cause a false positive result.
Miscarriages, abortions, and biochemical pregnancies are also potential causes of false positive test results. With all three situations, your body may still contain trace levels of the pregnancy hormone. While these trace levels may not be detected with a home pregnancy test, the blood test may give a false positive result.
Your pituitary gland also produces a hormone that shares many characteristics with the pregnancy hormone. It is possible for high levels of this pituitary hormone to provide false positive results.
In some cases, your doctor may follow the positive blood test with a urine test if he or she suspects that you are not pregnant. The urine may not contain antibodies that can interfere with the quantitative or qualitative blood test.
False negative results are less common. However, in some cases, your body may take longer to begin producing enough of the pregnancy hormone for detection in your blood.
If you think that you may be pregnant and get a negative result, you may request another blood test in a few days. The extra few days should provide enough time for your body to produce more of the pregnancy hormone.
Conclusion: Which Pregnancy Test Should You Use?
Home pregnancy tests are still relatively accurate and a useful way for women who miss a period to detect pregnancies. They are most accurate when they are used correctly, which means that you need to wait a couple of days after your missed period to take the test.
Whether you get a positive or negative result, most doctors recommend that you take a second home pregnancy test the following day. If you get two positive results, you should schedule an appointment with your doctor. Your doctor will likely use a blood test to verify the results of the home pregnancy test.
If you are undergoing IVF or IUI treatments, home pregnancy tests may not provide the most accurate results. After the treatment, your doctor should schedule you to come back in about two weeks for a blood test. If you take a home pregnancy test sooner, you may get a false positive or negative result.
In the end, blood tests are the most accurate option. They also provide earlier results. While home pregnancy tests provide a suitable solution for home detection, they should be verified with blood tests.