Blood Test for Pregnancy: Types, Results, Risks & Accuracy

Blood Test for Pregnancy Confirmation – How Does It Work?

If you and your spouse were planning to start a family and suspect that you are pregnant, chances are that you’ve already taken a home pregnancy test. If the test says positive, then you must be ecstatic. But the journey has just begun. You will now have to see a doctor to confirm your pregnancy. The doctor will suggest a blood test for the same. The best way to confirm a pregnancy is via a blood test. Blood tests are also done in the early stages of pregnancy to ensure a healthy and happy journey into parenthood.

What Is a Blood Pregnancy Test?

A blood pregnancy test is done to determine whether a woman is carrying a child or not. It is the first step in the journey of parenthood.

Several factors are accounted for in a blood pregnancy test:

  • A urine test which can be taken at home whereas a blood pregnancy test needs to be taken by a specialist in a clinic or a diagnostic centre.
  • A blood pregnancy test is taken to know for sure if a woman is pregnant.
  • It is used to test for the levels of hCG or pregnancy hormone in the body which only elevates if you are pregnant.
  • To take this test, some amount of blood sample is extracted from the woman and then tested for hCG.
  • The hormone human chorionic gonadotropin (hCG) is detected around 8-10 days after conception.

Why Should You Choose a Blood Test to Confirm Pregnancy?

While it is easy to take a home pregnancy test which is a urine-based test, it is not always accurate as the time period from conception to the time of next menstruation is not clear. A blood test gives the exact result and also helps to identify and confirm the pregnancy early.

Types of Blood Test to Check Pregnancy

There are two types of blood tests used to determine pregnancy. Depending on when it is taken, it could either be a negative blood pregnancy test or a positive blood pregnancy test.

The two types of blood pregnancy tests are:

  1. Qualitative hCG Blood Test– This is to know if the pregnancy hormone is being produced in the body or not.
  2. Quantitative hCG Blood Test– This test is done 48 hours apart to determine a specific level of HCG to be measured in the body.

Qualitative Blood Serum Test

There is a procedure called venepuncture which is used to extract the blood sample from the vein for a qualitative blood test. It is instant and is only done once to detect the level of hCG in the blood.

Quantitative Blood Serum Test

A venepuncture is used in this type of test as well to detect pregnancy and blood is drawn twice in a span of 48-72 hours to check for pregnancy. This test also looks for hCG levels in the blood and is more accurate as there is a waiting window before the next test in case of a false negative result the first time.


How Is the Test Performed?

The pregnancy blood test is performed by a technician or nurse who first draws blood from a vein which is usually located by identifying in the forearm or hand. The blood is collected by using a syringe or vial. The blood test is usually performed at a separate diagnostics lab and then sent to a doctor, or you may have to go collect the reports. The test usually identifies and determines the level of HCG or pregnancy hormone in the blood.

How Are the Test Results Interpreted?

Results from a quantitative hCG test can showcase raising levels of hCG in the first trimester of pregnancy and then it starts to decline.

Some interpretations of the test are:-

  1. The presence of more than one fetus, i.e. twins or triplets
  2. If there is a sign of ovarian cancer
  3. Non-cancerous tumours of the uterus
  4. Infection or malignant tumour of the uterus

If the levels of hCG are less than normal, it can also indicate

  1. Possible death of the foetus
  2. An incomplete or complete miscarriage
  3. An ectopic pregnancy

How Accurate Are Pregnancy Blood Test Results?

The blood pregnancy tests are 98-99% accurate if they are performed around 7 days after ovulation, a week prior to the period being due. Although there are chances of false-negative results and false-positive results too.

False-negative results

This means that you are actually pregnant, but the test results show that you are not. This usually occurs if the test is taken too early, i.e. it is difficult to detect the levels of HCG in the blood thereby leading to a negative. If you think this is not an accurate result and you feel pregnant, you should repeat the test within 48-72 hours.

False-positive results

This means that you are not pregnant and the test has shown that you are which is a rarity. This result can happen if you are under certain medication or have a certain medical condition which causes a higher level of hCG.

Medication That Can Affect the Accuracy of the Results

There are several medications that can affect the accuracy of a blood test taken for pregnancy. Some of them are listed below:

  1. Hypnotics- Prescription of sleep medication can affect levels of hCG.
  2. Promethazine- A medication used to treat allergic symptoms, cold or a cough or motion sickness can increase or decrease levels of hCG.
  3. Medication to prevent seizures.
  4. Any medicines are taken to treat Parkinson’s disease.
  5. Any prescription that contains hCG like Pregnyl, APL, Profasi, Chorex, Novarel, or Ovidrel
  6. Phenothiazine drugs such as Chlorpromazine or Thorazine

How Soon Can Blood Test Detect Pregnancy?

If you are wondering how soon can a blood test detect pregnancy after conception, or if you and your partner have been trying to have a child and you feel like you could be pregnant it is time to take a blood test to detect pregnancy right after you miss your first period.

  1. HCG, which is produced when the implantation in the placenta takes place, can be detected in the blood as early as 10 days after a missed period. This is when you know when to take a blood pregnancy test.
  2. The levels of hCG rise exponentially during the first two months of pregnancy. The rapid shift in the hormones makes it easy to detect pregnancy through a blood test 10-12 days after conception.
  3. If you have taken a blood test to determine pregnancy, you will have to wait a day or two for the reports to arrive from the diagnostics centre.
  4. In the early stages of pregnancy, blood is drawn at least 48 hours apart to determine hCG. The hormone doubles every 48 hours so reading will be accurate if you are pregnant.


Risks of Taking a Pregnancy Test Using Blood

Nowadays the risks involved in taking blood-based pregnancy tests are next to none as it is quite regulated. Some of the risks are

  1. The biggest risk of taking a blood test for pregnancy is false positive which can occur due to different medications being taken by the mother
  2. Light bruising where the needle is inserted
  3. Lightheadedness
  4. Fainting (rare)
  5. Infection (rare)
  6. Haematoma which happens when the blood accumulates under the skin.

Can a Blood Pregnancy Test Be Wrong?

If you get an early pregnancy blood test, the chances are that they may be sometimes false even if you are pregnant.

  1. Blood tests are usually 98-99% accurate as it takes time for the pregnancy hormone to rise in the blood, depending on the time from the date of conception.
  2. However, medication and many other factors could affect the accuracy of the test. It is always good to take the test again in 10 days time if you still haven’t got your periods.
  3. Situations where women are on fertility drugs, the test will show a false positive where it detects hCG levels present due to the treatments.

Can You Perform This Test At Home?

A blood pregnancy test needs to be taken at a gynaecologist’s clinic or at a diagnostics centre and cannot be taken at home.

If you have an intuition that you could be pregnant, you can take a home pregnancy test or a urine test initially. But you must get a blood test done to confirm the pregnancy. It is also important to mentally prepare oneself for the journey of parenthood as it’s a big responsibility.

Also Read:

Right Time and Way to Take Pregnancy Test
Faint Line on Pregnancy Test

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