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As your pregnancy progresses, your body goes through constant changes, and blood tests help track those changes carefully. They can indicate whether your iron levels are low, whether there is an infection, or whether your body needs extra care at any stage. Many issues do not show obvious symptoms at first, which is why these tests are so important.
Blood Tests During Pregnancy: First Trimester
During the first trimester, blood tests are mainly done to understand how your body is doing and to catch any possible concerns early on.- Complete blood count: It looks at different components of your blood, including red blood cells, white blood cells, haemoglobin, and platelets. They help identify if you’re low on iron and at risk of anaemia, if there’s any sign of infection, or if your blood is clotting the way it should.
- Blood type and Rh factor: Knowing your blood type and whether you are Rh-negative or Rh-positive is essential. If you are Rh-negative, there might be a chance of incompatibility with the baby, which can lead to complications. But early knowledge allows for proper management.
- Screening for infections (HIV, Hepatitis B, and Syphilis): These blood tests are done to check for certain infections that can be passed from mother to baby during pregnancy or at the time of birth.
- Rubella immunity: This test checks whether your body is protected against rubella, also called German measles. Many people are immune due to childhood vaccination, but it’s important to confirm immunity. Catching rubella during pregnancy can be very harmful for the baby, as it can cause serious birth defects.
- First-trimester screening blood tests: These tests are usually done as part of a combined screening in early pregnancy. They measure two important substances in your blood: pregnancy-associated plasma protein A (PAPP-A), which is produced by the placenta, and human chorionic gonadotropin (hCG), a hormone also released by the placenta. If the levels of these are higher or lower than expected, it can suggest a higher risk of chromosomal conditions such as Down syndrome or trisomy 18. This is often done alongside an ultrasound.
- Cell-free foetal DNA testing: From around 10 weeks of pregnancy, this test may be offered as an option. It is a non-invasive blood test that looks for small fragments of the baby’s foetal DNA circulating in your blood. By analysing this DNA, the test screens for chromosomal abnormalities, including Down syndrome, trisomy 18, and trisomy 13.
Blood Tests During Pregnancy: Second Trimester
As your baby starts growing more rapidly, blood tests in the second trimester focus more on detailed screening and risk assessment.- Multiple marker or quad screen: This test is usually done between 15 and 20 weeks of pregnancy. It measures four different markers in your blood. The first is alpha-fetoprotein, which comes from the baby’s liver and can signal neural tube defects, abdominal wall issues, chromosomal abnormalities, or even twins. It also checks estriol, a hormone from the placenta linked to foetal health. Inhibin, another placental hormone, and hCG are also measured. Together, these help assess risks of genetic conditions or birth defects such as spina bifida.
- Glucose challenge or screening: Around 24 to 28 weeks, you will have a test to check sugar levels in your blood. High results might suggest gestational diabetes, which affects both you and your baby, and could lead to a follow-up glucose tolerance test for confirmation.
- Antibody screening: If you are Rh-negative, this blood test is repeated later in pregnancy to check whether your body has made any antibodies against the baby’s blood cells.
Blood Tests During Pregnancy: Third Trimester
As you move closer to delivery, blood tests in the third trimester focus on preparing your body for birth.- Repeat complete blood count: You may have this again to monitor for anaemia, which becomes more common as pregnancy advances. This is to make sure you stay strong for delivery.
- Rh antibody testing: If you are Rh-negative, this test is repeated around 28 weeks or later to make sure no harmful Rh antibodies have developed. If there is any risk, doctors can provide preventive treatment to prevent complications.
Understanding Your Blood Test Results During Pregnancy
Blood screenings performed during pregnancy are primarily intended to assess risk, not to provide a definitive diagnosis. Sometimes results can show a false positive or false negative, meaning the test may indicate a concern when everything is fine, or miss something that is actually present. That’s why your doctor may recommend additional tests, such as an ultrasound or other screenings, to get a clearer picture.These blood tests play a big role in making your pregnancy safer. The exact options available to you depend on your personal situation, so always discuss them with your doctor. Staying on top of them supports the healthiest possible outcome for you and your little one!
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FAQs on The A-Z of Blood Tests Needed in Every Pregnancy Trimester
- Are all blood tests mandatory during pregnancy?
Not every blood test is compulsory. Some are routine and strongly recommended, while others are optional screenings. - Will I need to fast before pregnancy blood tests?
Only a few pregnancy blood tests require fasting, mainly the fasting blood sugar test and the oral glucose tolerance test (OGTT) for gestational diabetes, which usually require 8 to 10 hours of fasting.
