Pregnancy Blood Test: Do I Need One?
- Most women do not need a blood test to confirm pregnancy
- At-home pregnancy tests (the urine-based ones) are very accurate when used properly
- During your pregnancy, your doctor will draw blood to check for infections and other conditions that can affect your baby
- New blood tests are being developed that can detect complications (such as preeclampsia and preterm birth)
If you suspect you may be pregnant, you might wonder if you need a pregnancy blood test. Do you really need to go to the doctor for a blood draw to confirm pregnancy? (And are pregnancy blood tests any different or better than the urine-based ones you take at home?)
Do I need a blood test to confirm pregnancy?
For most women, seeing a doctor for a blood test to confirm pregnancy isn’t necessary. Urine-based home pregnancy tests are very accurate when performed correctly. Usually, early pregnancy blood tests are given for peace of mind, but in some cases, your doctor will want a blood test to measure your hCG level. If your doctor suspects an ectopic pregnancy, they will take action right away. Or if your progesterone levels are low, you may be given progesterone in early pregnancy, which may reduce the risk of miscarriage for some women who have recurrent miscarriages.
It’s important to note here that doctor’s urine-based pregnancy tests are not any more sensitive than the ones commercially available in drug stores. Doctors know this—and it explains why they will usually say you don’t need to come in for your first visit until you are further along.
The takeaway? At home pregnancy tests are so reliable, even doctors trust them.
How early can pregnancy be detected with a blood test?
A blood test can detect pregnancy within 1 day of implantation or even potentially less. The primary benefit of pregnancy blood tests is their sensitivity. A urine-based pregnancy test will usually detect pregnancy around 3-4 days after implantation, though it sometimes takes longer.
What are the different types of pregnancy blood tests?
There are two types of pregnancy blood tests: a qualitative blood serum test and a quantitative blood serum test. Both involve analyzing a small sample of your blood.
Qualitative Blood Serum Test:
- This blood test confirms if the pregnancy hormone, hCG, is present. Much like a urine-based home pregnancy test, this test will give you a “yes” (you’re pregnant) or a “no” (you’re not pregnant) result.
- Even though these pregnancy blood tests are very accurate and sensitive, if a qualitative blood serum test is taken too early, you may still receive a false negative.
Quantitative Blood Serum Test:
- Also known as the beta hCG test, this test measures the exact amount of hCG in your blood, making it the most accurate pregnancy blood test.
Are these tests more accurate than the home pregnancy tests?
Both pregnancy blood tests and home pregnancy urine tests test for the same hormone, human chorionic gonadotropin, or hCG. The body begins producing hCG as soon as a fertilized egg successfully undergoes implantation. The hCG level doubles roughly every 48 hours. The best home pregnancy tests are able to detect hCG approximately 12 – 14 days after implantation.
You can take a urine-based pregnancy test in the comfort of your home, and many of them claim to be 99% accurate when performed correctly, making them more convenient than a pregnancy blood test.
If you’re asking yourself, “How do I get a blood test for pregnancy?” these tests are performed in a doctor’s office or lab, and you will need to wait longer for pregnancy blood work results. Depending on where you live or your type of medical insurance, this may cost money as well as time.
Is it possible to get a false positive?
Pregnancy blood tests are very accurate. While it is occasionally possible to get a false negative result, false positives are very rare. A false positive blood test usually occurs when you’re taking medications that contain or increase the amount of hCG in your blood. Before, during, and after pregnancy, you should always discuss every medication you’re taking with your doctor.
Which blood tests are done during pregnancy?
During your prenatal visits, you will be given blood tests to check for infections or other conditions that could potentially harm your baby.
Your doctor may screen your blood to look for:
Rh factor is a protein that found on the surface of your red blood cells. If your blood cells have this particular protein, you are considered “Rh positive.” If your blood cells do not have this protein, you are considered “Rh negative.” If you are Rh-negative and your fetus is Rh positive, it can cause problems during pregnancy because your body can produce antibodies against your baby’s blood.
This is called Rh incompatibility, and while it won’t hurt your current pregnancy, it can cause problems for future pregnancies if it’s not treated. If you have this incompatibility, your doctor will give you a shot of Rh immunoglobulin (RhIg), a blood product that can prevent sensitization of an Rh-negative mother.
Many women develop an iron deficiency during pregnancy. This is because the body needs extra iron so that the baby has a sufficient blood supply and can receive the necessary oxygen and nutrients. So, if your doctor detects an iron deficiency, you may need to take an iron supplement.
A blood test can also reveal infections that may affect your baby, such as:
- Hepatitis B
- Hepatitis C
Gestational diabetes (GDM) is a type of diabetes that can affect some women during pregnancy. It develops when there is too much glucose (sugar) in the blood. Gestational diabetes tends to develop in the third trimester (after 28 weeks) and usually disappears after the baby is born.
What developments have been made in pregnancy blood tests?
There are exciting new developments in prenatal blood tests, which expand the scope of their benefits. New research has shown that blood tests can predict premature birth and may identify the risk of gestational diabetes in the first trimester. In both cases, forewarned is forearmed: The sooner doctors can begin preparing for a potentially risky pregnancy, the better the overall outcomes. By addressing risks earlier in the pregnancy, you may be able to deal with concerns and make lifestyle changes before reaching a health-related crisis.
Recent research out of Australia also indicates that blood tests may be used to determine a mother’s risk of preeclampsia, a severe and possibly life-threatening pregnancy complication related to high blood pressure that effects 3 – 8% of pregnant women. Although the test for preeclampsia is not currently available in the United States, its use in Australia—where it accurately predicted preeclampsia in 95% of cases—indicates that positive steps are being taken. Be sure to ask your doctor about the latest available tests.
When should I talk to my doctor?
For most women, your doctor or ob-gyn will expect to see you approximately eight weeks into your pregnancy. If you have concerns that require testing for pregnancy very early, or if you have previously suffered a miscarriage or ectopic pregnancy, you should consider going to your doctor as soon as possible, as they will be able to perform an ultrasound or order a quantitative blood serum test to help determine if your pregnancy is progressing normally.