Testing for Pregnancy >> Blood Pregnancy Test
You are now several days post ovulation and you suspect that this might be the cycle that you conceived! The next question that you might ask yourself is: should I run to the doctor for a blood pregnancy test or should I take a home pregnancy test?
Like most questions related to fertility and pregnancy, there is no straightforward answer to this question. Both a blood pregnancy test and a home pregnancy test will identify the presence of the pregnancy hormone called human chorionic gonadotropin (hCG), and will determine if you are pregnant or not. So, to determine which test is right for you, you might want to consider convenience, expense, accuracy, and your fertility history.
There are actually two different types of blood pregnancy tests, also called pregnancy serum tests. One type, called a quantitative blood pregnancy test (or a beta hCG test), measures the exact amount of hCG in the blood, while a qualitative blood pregnancy test simply provides confirmation of the presence of hCG, and a "yes" or "no" answer for pregnancy. If the blood pregnancy test reveals that hCG is under 5 mIU/ml, then the test will be considered negative. If the level of hCG is determined to be between 5 and 25 mIU/ml, this is said to be an equivocal result, and another test should be performed in a few days to confirm pregnancy.
As for home pregnancy tests, there are several types to choose from. All home pregnancy tests (HPT) detect the presence of hCG in urine, and come either in a test strip, midstream or digital format. With the test strip or midstream format, you will dip the strip in a urine sample or urinate directly on the stick, wait a few minutes, and watch for the appearance of a colored test line to appear, which indicates a positive result. A digital test will typically provide a definitive "no" or "yes" in words that appear on the digital display. Each unique HPT is calibrated to detect a specific level of hCG in the urine, such as 20 mIU/ml, 50 mIU/ml or 100 mIU/ml. More "sensitive" tests, those that are able to detect a lower amount of hCG, can provide an accurate result as early as 7-10 days post ovulation.
When deciding if you should use an HPT or have a blood pregnancy test done at the lab, here are a few items to consider:
- Convenience: While it is true that a quantitative blood test can confirm pregnancy a couple of days before an early detection HPT, a qualitative blood test that is set to detect 25 mIU/ml is no more sensitive than an early detection HPT. Many women find it more convenient to simply wait a day or two and take a pregnancy test in the privacy of their home. In addition, an HPT will typically produce results in just minutes. On the other hand, you might be on pins and needles for up to 48 hours while you wait for results from a blood pregnancy test.
- Expense: The out of pocket expense for a blood pregnancy test will vary depending on the clinic you choose and the type of insurance you have. You should expect to pay up to about $75 for this service. And, if the results are uncertain (hCG level between 5 mIU/ml and 25 mIU/ml), a retest will be required in a few days, which will in most cases incur an additional fee. On the other hand, you can purchase 10 early detection pregnancy test strips for about $10, which will allow you to test several days in a row if necessary.
- Accuracy: The most "accurate" pregnancy test is the quantitative blood pregnancy test, as it determines the exact amount of hCG in your blood. This will allow your doctor to make a very clear determination about whether or not you are pregnant or if a retest is required in a few more days. With both a qualitative blood test and an HPT it is possible to get a false negative result. This means that if the test is not sensitive enough to detect your current level of hCG (for example, your current level is 20 mIU and the test is set to detect hCG at 25 mIU), you will get a negative test result even though you are pregnant. If you get a negative result from an HPT or a qualitative blood test, and you continue to have any signs of pregnancy, we recommend retesting in a few days.
- Fertility history: If you have experienced a miscarriage or an ectopic pregnancy in the past, your doctor may well want to monitor your hCG levels closely in the first several weeks of pregnancy. In the early days of pregnancy, hCG levels double every 48-72 hours. (See the chart below for average blood hCG levels as pregnancy advances). If hCG levels do not rise appropriately in those very early days, it can signal a problem with the pregnancy. By monitoring your exact hCG levels with regular quantitative blood test, your doctor may be able to detect a problem early on. Neither a qualitative blood test nor an HPT allows this type of monitoring, as they do not reveal exact amounts of hCG, and cannot determine if levels are increasing appropriately.
The following is a list of blood hCG levels achieved as pregnancy advances (LMP means last menstrual period):
- 3 weeks since LMP: 5 - 50 mIU/ml
- 4 weeks since LMP: 5 - 426 mIU/ml
- 5 weeks since LMP: 18 - 7,340 mIU/ml
- 6 weeks since LMP: 1,080 - 56,500 mIU/ml
- 7 – 8 weeks since LMP: 7,650 - 229,000 mIU/ml
- 9 – 12 weeks since LMP: 25,700 - 288,000 mIU/ml
- 13 – 16 weeks since LMP: 13,300 - 254,000 mIU/ml
- 17 – 24 weeks since LMP: 4,060 - 165,400 mIU/ml
- 25 – 40 weeks since LMP: 3,640 - 117,000 mIU/ml
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