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Taking a Blood Test for Pregnancy

Can a blood test detect a pregnancy? The answer is “yes” but it is much rarer to take a blood test for pregnancy these days now that accuracy can be achieved with sensitive home pregnancy tests. Sensitive urine tests cost less than blood tests (unless it is free under your insurance plan) and can tell you your results several days before you miss your period in the comfort of your own home. The earliest you can test for pregnancy is after implantation has occurred and even then the test can be inconclusive if you test too early or have an ectopic pregnancy that naturally has low levels of HCG.


Can a blood pregnancy test be wrong? A blood test can only be wrong if you have some kind of condition, such as an HCG-secreting tumor that secretes abnormal HCG levels from the tumor instead of a pregnancy. This type of false positive pregnancy test is very rare so you can assume for the most part that, if you have a positive pregnancy test to determine pregnancy status, you are really pregnant until proven otherwise. Most of the time an ultrasound can confirm that you are in fact pregnant at some point in early pregnancy with accurate dates.

Can a blood test detect a pregnancy? The answer is “yes” but it is much rarer to take a blood test for pregnancy these days now that accuracy can be achieved with sensitive home pregnancy tests. Sensitive urine tests cost less than blood tests (unless it is free under your insurance plan) and can tell you your results several days before you miss your period in the comfort of your own home. The earliest you can test for pregnancy is after implantation has occurred and even then the test can be inconclusive if you test too early or have an ectopic pregnancy that naturally has low levels of HCG.


Can a blood pregnancy test be wrong? A blood test can only be wrong if you have some kind of condition, such as an HCG-secreting tumor that secretes abnormal HCG levels from the tumor instead of a pregnancy. This type of false positive pregnancy test is very rare so you can assume for the most part that, if you have a positive pregnancy test to determine pregnancy status, you are really pregnant until proven otherwise. Most of the time an ultrasound can confirm that you are in fact pregnant at some point in early pregnancy with accurate dates.

Having a Pregnancy Blood Test

Many women wonder whether to have a blood vs urine pregnancy test. In general, these tests give similar results although a quantitative HCG test cannot be done with a urine test. Only a blood test for pregnancy can be done with quantitative HCG results given. A quantitative HCG test can tell if a pregnancy is healthy because the number you receive should double if you repeat the test in 48 hours and have a healthy pregnancy. During pregnancy testing using blood, it can be nerve-wracking to wait the 48 hours but it is the best way to know early on if the pregnancy is healthy.
How to get a blood pregnancy test? You can have this kind of testing done at Planned Parenthood or at your OB/GYN doctor’s office if there is a question as to whether or not the pregnancy is viable. This kind of test can’t determine the gender of your baby yet but after a couple of months you will be able to do that, too. Some people wonder “where can I get a blood pregnancy test if I have no insurance.” There are free clinics in just about any major city where you can have a blood pregnancy test for no or low cost. How much does a blood pregnancy cost? It depends on your insurance. There may be a copay for lab work or you may not have coverage for this kind of lab test. In such cases, a blood test for pregnancy can cost around $50 in out of pocket expenses.

Taking a Blood Test for Pregnancy

If you choose to determine pregnancy status with a blood test, you will have to make an appointment to see your doctor. A sample of blood will be taken for determination of pregnancy. How long does a pregnancy test take? A qualitative pregnancy test for pregnancy takes only a few minutes, while a quantitative test takes up to a couple of hours. How accurate are blood pregnancy tests? They are very accurate and can tell you if you are pregnant up to 6 days before a missed menstrual period. As long as implantation has happened and HCG is in the maternal serum, the quantitative blood test will show higher than normal levels of HCG in the maternal serum and can indicate a very early pregnancy.
The downside of having such sensitive testing is that you can have an unhealthy pregnancy that will show a small amount of HCG in the urine. You may falsely believe you have a healthy pregnancy but the HCG level will remain low and you will have a miscarriage or ectopic pregnancy somewhere down the line. You can’t really tell if the pregnancy is healthy by one quantitative HCG test. It takes at least two HCG tests done 48 hours or so apart in order to determine that the pregnancy is developing normally. This kind of testing can be done well before an ultrasound can tell if the pregnancy is going to progress normally.

How does a Blood Pregnancy Test Work?

A quantitative blood test for pregnancy measures the amount of HCG in your bloodstream. Normally, this is negligible if you aren’t pregnant. After implantation, the HCG leaches from the embryo into the maternal serum and the HCG levels rise. Levels as low as 25 mIU/ml can be positive in some sensitive urine tests but a blood test can actually show levels below that number. The actual value of the HCG level in the blood can vary with the pregnancy. The important thing isn’t the absolute value of the HCG test but rather that the HCG level should steadily rise and should ideally double every 48 hours in a healthy pregnancy. Levels that stay the same or drop can indicate an ectopic pregnancy or impending miscarriage.

After Positive Pregnancy Test

At the first prenatal visit, the doctor may repeat the pregnancy test if there is some question as to whether or not you are really pregnant. If you are pregnant, a variety of routine blood tests and genetic tests may follow. For example, a CBC, rubella titer, RPR and possibly an HIV test will be done at the first prenatal visit along with your blood type to see if you are Rh positive or Rh negative.

As the pregnancy proceeds, you may decide to have genetic testing done. This is done through chorionic villous sampling or an amniocentesis. These are tests done in the late first trimester (CVS testing) or in the middle of the second trimester (amniocentesis testing). Both tests will check for chromosome abnormalities such as Down syndrome and Trisomy 18 and may check for other genetic diseases as well, such as cystic fibrosis. These tests also tell you the gender of your baby with 100 percent accuracy. If you don’t have these tests done, you will be able to have a determination of the gender of the baby and determinations of obvious birth defects during an ultrasound done around 18-20 weeks gestation. Ultrasounds aren’t 100 percent accurate but the latest ones are nearly as accurate as an amniocentesis and are much less invasive than having CVS or amniocentesis tests performed.

Later on in the pregnancy, you will have glucose testing done that will check for gestational diabetes. In this test, you will receive a 50 gram glucose load by mouth and your blood sugar will be tested after one hour. If this test is too high, you may have further testing that might indicate you have gestational diabetes during this pregnancy. Just because you have gestational diabetes during one pregnancy doesn’t automatically mean you will have it during subsequent pregnancies but your risk for this will be higher than average.
Routine blood tests are part of every pregnancy. You won’t likely have a blood test at every pregnancy visit but at various intervals, your hemoglobin or hematocrit will be tested to see if you have become anemic during the pregnancy and need extra iron supplementation.

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