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How to prevent Rh conflict during pregnancy?
Medical expert of the article
Last reviewed: 06.07.2025
[ Mechanism of action of anti-Rh0(D)-immunoglobulin
It has been shown that if an antigen and its antibody are injected together, no immune response is observed, provided that the antibody dose is adequate. By the same principle, anti-Rh0(D) immunoglobulin (antibody) protects against an immune reaction when a Rh-negative woman is exposed to Rh(+) [D(+)] fetal cells (antigen). Anti-Rh0(D) immunoglobulin has no negative effect on the fetus and newborn. Anti-Rh0(D) immunoglobulin does not protect against sensitization with other Rh antigens (other than those encoded by the D, C, and E genes), but the risk of hemolytic disease of the fetus caused by antibodies to antigens of the Kell, Duffy, Kidd, and other systems is significantly lower.
A dose of 300 μg of anti-Rh0(D) immunoglobulin administered at 28 weeks of gestation reduces the risk of isoimmunization during the first pregnancy from 1.5 to 0.2%. Therefore, at 28 weeks of gestation, all Rh-negative non-immunized pregnant women (no antibodies), when the father of the fetus is Rh-positive, should receive prophylactic 300 μg of anti-Rh0(D) immunoglobulin.
If prophylaxis during pregnancy at 28 weeks was not carried out, then each unimmunized woman with Rh-negative blood is given 300 mcg (1500 IU) of anti-Rh0(D)-immunoglobulin within 72 hours after delivery of a child with Rh-positive blood. The same tactics are followed if for one reason or another the Rh-type of the child cannot be determined.
Administration of anti-Rh0(D) immunoglobulin to Rh-negative non-immunized women during pregnancy is necessary after procedures associated with the risk of fetal-maternal transfusion:
- artificial termination of pregnancy or spontaneous abortion;
- ectopic pregnancy;
- evacuation of hydatidiform mole;
- amniocentesis (especially transplacental), chorionic biopsy, cordocentesis;
- bleeding during pregnancy caused by premature detachment of a normally located placenta or placenta previa;
- closed trauma of the mother's peritoneum (car accident);
- external version in breech presentation;
- intrauterine fetal death;
- accidental transfusion of Rh-positive blood to an Rh-negative woman;
- platelet transfusions.
For pregnancy up to 13 weeks, the dose of anti-Rh0(D) immunoglobulin is 50–75 mcg; for pregnancy over 13 weeks, it is 300 mcg.
Administration of anti-Rh0(D)-immunoglobulin
Anti-Rh0(D)-immunoglobulin is administered intramuscularly into the deltoid or gluteal muscle, strictly, otherwise, if it enters the subcutaneous fat, absorption will be delayed. The standard dose of 300 mcg (1500 IU) of anti-Rh0(D)-immunoglobulin covers feto-maternal bleeding in the amount of 30 ml of whole Rh-positive blood or 15 ml of fetal erythrocytes.
Anti-Rh0 immunoglobulin dose adjustment
Required when significant feto-maternal bleeding is suspected.
The Kleihauer-Betke test is used to determine the number of fetal erythrocytes in the maternal circulation. If the volume of feto-maternal bleeding does not exceed 25 ml, 300 μg of anti-Rh0(D) immunoglobulin is administered (standard dose), with a volume of 25–50 ml – 600 μg.
The indirect Coombs test allows one to determine freely circulating anti-D antibodies or Rh immunoglobulin. If the required amount of anti-Rh0(D) immunoglobulin is administered, a positive indirect Coombs test (excess free antibodies) is determined the following day.
It is necessary to increase the dose of anti-Rh0(D)-immunoglobulin in the following cases:
- cesarean section;
- placenta previa;
- premature detachment of the placenta;
- manual separation of the placenta and removal of the afterbirth.
Prevention may be ineffective in the following situations:
- the dose administered is too small and does not correspond to the volume of feto-maternal bleeding; the dose is administered too late. Anti-Rh (D) immunoglobulin is effective if used within 72 hours after delivery or exposure of the mother to Rh-positive cells;
- the patient has already been immunized, but the level of antibodies is lower than that required for laboratory determination; non-standard anti-Rh (D) immunoglobulin (insufficient activity) was administered to neutralize fetal red blood cells that have entered the mother's body.
Patient education
Every woman should know her blood type and Rh factor, as well as her partner's blood type and Rh factor before becoming pregnant.
All women with Rh-negative blood should be informed about the need for prophylactic use of anti-Rh immunoglobulin in the first 72 hours after childbirth, abortions, miscarriages, ectopic pregnancy from a Rh-positive partner. Despite the positive effect of prophylaxis with anti-Rh immunoglobulin, artificial termination of pregnancy (abortion) is undesirable due to the risk of immunization in a woman with Rh-negative blood from a partner with Rh-positive blood, especially after 7 weeks of pregnancy.