Antenatal Blood Investigations

(Content revised 01/2020)(Reprinted 01/2021)

During the first antenatal visit, the following blood tests are offered to pregnant women:

  1. Blood Grouping

    It is important to know the blood group of the pregnant woman in case she needs a blood transfusion. The four main blood groups are O, A, B and AB.

  2. Rhesus (Rh) Factor

    Rh factor is an antigen found in red blood cells. Individuals who possess this factor are classified as ‘Rh positive' and those without it as ‘Rh negative'.

    Majority of the Chinese population are Rh positive. When a Rh negative mother is carrying a Rh positive foetus, problems can occur in the foetus such as haemolytic anaemia, oedema or even death. Regular blood test will then be needed.

  3. Haemoglobin and Mean Cell Volume

    These tests help to find out whether the pregnant mother has anaemia. Mean cell volume (MCV) is a simple and easy test which helps to find out who has a higher chance of carrying the thalassaemia genes or iron deficiency anaemia. Please refer to “Mean cell volume & Thalassaemia” leaflet for details.

  4. Rubella Antibody

    A woman who has received Rubella vaccine or contracted Rubella before conception should have developed immunity, that is, having Rubella antibodies. This can protect her from contracting Rubella during pregnancy. Rubella infection may cause foetal abnormalities. If the woman does not have Rubella antibody, she should receive Rubella vaccine after delivery.

  5. Hepatitis B Antigen

    About eight percent (8%) of the local population are Hepatitis B Virus carriers. Most of these carriers show no signs or symptoms of the disease. If the blood test is positive for Hepatitis B antigen, then the mother is a carrier. A mother who is a Hepatitis B carrier may transmit the virus to the infant at or around the time of delivery. The newborn should receive Hepatitis B vaccine and Hepatitis B immunoglobulin after birth so as to protect him against Hepatitis B infection.

    For more information, please visit the website of the Viral Hepatitis Control Office of the Department of Health.

  6. Syphilis

    Untreated syphilis in pregnancy may result in miscarriage or cause foetal congenital defects such as blindness or deafness. Therefore, early detection and treatment are necessary.

  7. Human Immunodeficiency Virus (HIV) Antibody Testing

    HIV can cause AIDS (Acquired Immune Deficiency Syndrome). The routes of transmission include sexual intercourse, blood contact or from an infected mother to her baby during pregnancy, delivery or breastfeeding. The transmission rate from an infected mother to her baby is 15%-40%. The transmission rate can be reduced to 1-2% with effective treatment and prevention given in the course of pregnancy, during delivery and to the baby after birth

Please contact medical staff if you have any queries concerning the above blood tests.