Testing of Antenatal Samples

Blood group typing and blood group antibody screening of pregnant mothers

All expecting mothers are screened for blood group antibodies in the early pregnancy and they are ABO and RhD typed at the same time. The Blood Service has been performing these screenings in a centralised manner since 1990. The purpose of the screening is to find those mothers, whose babies are at a risk of developing haemolytic disease of the fetus and newborn.

Pregnant mothers are screened in accordance with the national programme in the following manner:

• A blood sample is taken from all mothers visiting the maternity clinic between 8 and 12 weeks of pregnancy.
• In addition, RhD negative mothers are screened between 24 and 26 weeks of pregnancy and during the 36th week of pregnancy, because they have an elevated risk of forming blood group antibodies.
• If an RhD positive mother has been given blood transfusions or her previous child has been treated for newborn jaundice, an additional sample is taken during the 36th week of pregnancy.
• If antibodies are found, their concentration is monitored at regular intervals.

The Blood Service screens the samples of approximately 60,000 mothers a year, and about 1 % of the mothers monitored for antibody concentration. Most of the tests are accredited (FINAS T119, EN ISO/IEC 17025, EN ISO 15189).

Fetal blood group determination

The blood group of the fetus can be determined for the targeting of anti-D prophylaxis. The fetal blood group is also typed in the case of severe blood group immunisation to help planning the treatment. 

Targeting of anti-D prophylaxis to pregnancies where the fetus is RhD positive:

• The RhD blood group of the fetus is determined from the plasma of an RhD negative mother.
• The test is performed between 24 and 26 weeks of pregnancy.

Planning of treatment in the case of severe blood group immunisation

• The Rh or Kell blood group of the fetus is determined from the amniotic fluid.
• The RhD blood group of the fetus is determined from the mother’s plasma.
• The tests are performed starting from the 16th week of pregnancy.