The Top Most Important Blood Tests to be done during Pregnancy

Right from the start of pregnancy, your gynecologist will recommend several blood tests with the objective of ascertaining you and your fetus’s health. The tests are a vital part of your pregnancy journey, as it allows your doctor to come up with a personalized pregnancy care plan.  Also, problems or complications can be diagnosed early on with their help so that you and your baby get the right treatment on time.Here is a list of the most important blood tests offered during pregnancy, why they are required and when they should be done.

  1. Blood group: This test determines your blood group, whether it is A, B, AB or O.

Importance: In case a need for blood transfusion arises due to heavy bleeding during pregnancy or childbirth, knowing the blood group is vital.

When: Done in the first trimester, usually in early pregnancy as a part of the first antenatal screening.

  1. Rh factor: Red blood cells have a surface protein called the Rhesus (Rh) factor. If present, you are Rh-positive or else you are Rh-negative.

Importance:  If you are Rh-positive, which is common, then there is no need to worry. But if you are Rh-negative and the baby is Rh-positive, this can lead to Rh incompatibility. Your body can produce Rh antibodies against the baby’s blood cells. Although not an issue during the first pregnancy, these antibodies can attack the baby’s red blood cells in subsequent pregnancies, which can become life threatening to the baby. If tested in time, the Rh immune globulin injection can help to protect your baby.

When: First trimester. If the mother is Rh-negative, the test is repeated in the second trimester, at 28 weeks, to check for Rh antibodies.

  1. Complete blood count (CBC) and other routine blood tests: Hemoglobin, hematocrit, Iron levels to check for anemia, information about blood cells, blood glucose to check for diabetes, lipid levels as well as thyroid gland functioning are measured.

Importance: These tests diagnose anemia (which is common during pregnancy), diabetes, infection, and other disorders. Severe anemia can result in preterm birth or a low birth weight baby. On-time treatment and lifestyle changes can be done to ensure a healthy pregnancy.

When: First trimester. Repeated in the second trimester around 26–28 weeks, mainly to check hemoglobin and platelet levels

  1. Sexually Transmitted Diseases and other Infections: Testing is done for Human Immunodeficiency Virus that causes AIDS, syphilis, herpes, hepatitis B and C, gonorrhea, Chlamydia and Rubella (German measles) antibodies.

Importance: These infections can lead to severe complications for the baby, including birth defects. Early diagnosis and treatment can prevent transmission to the fetus.

When: Done in the first trimester

  1. Human chorionic gonadotropin (hCG) hormone and Pregnancy-associated plasma protein screening (PAPP-A): The tests measure hCG and PAPP-A, which are produced by the placenta during early pregnancy.

Importance: Abnormal levels are associated with an increased risk of the fetus for chromosomal abnormalities like Down syndrome (trisomy 21) or Edwards syndrome (trisomy 18)

When: Done in the first trimester

  1. Multiple Markers: Depending on the number of markers screened, it is called Quad test (4 markers) or Triple test (3 markers). The following markers are tested:

                        a) Alpha-fetoprotein (AFP): a protein made by the baby’s liver

                        b) Human chorionic gonadotropin (hCG): a hormone produced by the placenta

                        c) Estriol (uE3): a hormone made by both placenta and fetus

                        d) Hormone inhibin A: produced by the fetus and the placenta

Importance: These tests screen for certain substances in the blood that determine the risk for genetic conditions or defects in the baby such as Down syndrome, spina bifida, or anencephaly. They are not diagnostic or completely accurate. Hence, they are considered along with the mother’s age, health history, ethnicity and other factors to determine a more than average chance of the baby having a birth defect. In case of abnormal results, additional testing such ultrasound and an amniocentesis are done for an accurate diagnosis.

When: Between 15 and 20 weeks of pregnancy, although 16-18 weeks is ideal


  1. Oral Glucose Tolerance Test: This test measures the blood glucose level to check for diabetes that occurs during pregnancy, known as gestational diabetes. It usually goes away after childbirth. Initially, a 1-hour glucose tolerance test is done, which, if abnormal, is followed by a 3-hour glucose tolerance test.

Importance: Gestational diabetes can give rise to severe complications like pre-eclampsia and infection. Treatment can ensure healthy childbirth.

When: Between 24 and 28 weeks of pregnancy


Thus, these most important blood tests done during pregnancy check for a wide range of conditions and also give a fair idea about your unborn baby’s health. Depending on your ethnic background and family history, your doctor might recommend other prenatal tests.


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