How to prevent Rhesus-conflict during pregnancy?
Last reviewed: 23.04.2024
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[The mechanism of action of anti-Rh0 (D) -immunoglobulin
It has been proved that if the antigen and its antibody are injected together, then there is no immune response, provided an adequate dose of antibodies is given. 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 does not have a negative effect on the fetus and the newborn. Anti-Rh0 (D) -immunoglobulin does not protect against the sensitization by other antigens of the Rh system (in addition to those encoded by the D, C and E genes), but the risk of hemolytic disease of the fetus caused by antibodies to Kell, Duffy, Kidd and others antigens is much lower.
A dose of 300 micrograms of anti-Rh0 (D) -immunoglobulin administered in 28 weeks of gestation, reduces the risk of isoimmunization during the first pregnancy from 1.5 to 0.2%. Therefore, in 28 gestation, all Rhesus-negative unimmunized pregnancies (no antibodies), when the fetus's father is Rh-positive, should receive 300 μg of anti-Rh0 (D) -immunoglobulin prophylactically.
If prophylaxis during pregnancy was not performed during the period of 28 weeks, then to each non-immunized woman with Rh-negative blood within 72 hours after birth at birth of a child with Rh-positive blood 300 μg (1500 IU) of anti-Rh0 (D) - immunoglobulin. The same tactics are followed if, for one reason or another, the Rh component of the child can not be determined.
The administration of anti-Rh0 (D) -immunoglobulin to Rh-negative nonimmunized women during pregnancy is necessary after procedures accompanied by the risk of maternal transfusion:
- induced abortion or spontaneous abortion;
- ectopic pregnancy;
- evacuation of cramps;
- amniocentesis (especially transplacental), chorion biopsy, cordocentesis;
- bleeding during pregnancy due to premature detachment of the normally located placenta or placenta previa;
- closed injury of the mother's peritoneum (car accident);
- external turn at a breech presentation;
- intrauterine fetal death;
- random transfusion of Rh-positive blood to the Rh-negative woman;
- transfusion of platelets.
If the pregnancy is up to 13 weeks, the dose of anti-Rh0 (D) -immunoglobulin is 50-75 μg, with a period of more than 13 weeks - 300 μg.
Introduction of anti-Rh0 (D) -immunoglobulin
Anti-Rh0 (D) -immunoglobulin is injected intramuscularly into the deltoid or gluteus muscle, strictly, otherwise, if it enters the subcutaneous adipose tissue, the absorption will be delayed. The standard dose of 300 μg (1500 IU) of anti-Rh0 (D) -immunoglobulin overlaps the fetal-maternal bleeding in a volume of 30 ml of whole Rh-positive blood or 15 ml of fetal erythrocytes.
Correction of the dose of anti-Rh0-immunoglobulin
Required for suspected significant maternal bleeding.
With the help of the Kleichauer-Betke test (Kleihauer-Wetke), the amount of fetal erythrocytes in the maternal circulation is established. If the volume of maternal bleeding does not exceed 25 ml, 300 μg of anti-Rh0 (D) -immunoglobulin (standard dose) is administered, with a volume of 25-50 ml - 600 μg.
Indirect Coombs test allows to determine free circulating anti-D-antibodies or Rh-immunoglobulin. If the required amount of anti-Rh0 (D) -immunoglobulin is administered, the positive indirect Coombs test (excess free antibodies) is determined the next day.
It is necessary to increase the dose of anti-Rh0 (D) -immunoglobulin at:
- Caesarean section;
- placenta previa;
- premature placental abruption;
- manual separation of the placenta and isolation of the placenta.
Prevention can be ineffective in the following situations:
- The dose administered is too small and does not correspond to the volume of maternal bleeding; the dose is too late. Anti-Rh (D) -immunoglobulin is effective if used within 72 hours after delivery or exposure to Rh-positive cells on the mother's body;
- the patient was already immunized, but the level of antibodies is less than necessary for laboratory determination, and non-standard anti-Rh (D) -immunoglobulin (insufficient activity) was introduced to neutralize the fetal erythrocytes penetrated into the mother's body.
Patient education
Every woman should know her blood group and Rh factor, as well as the blood group and the partner's Rh factor before pregnancy.
All women with Rhesus-negative blood should be informed of the need for preventive use in the first 72 h of anti-Rhesus immunoglobulin after childbirth, abortion, miscarriage, ectopic pregnancy from a Rh-positive partner. Despite the positive effect of prophylaxis with antiresus immunoglobulin, it is undesirable to artificially terminate pregnancy (abortion) because of the risk of immunization in a woman with Rh-negative blood from a partner with Rh-positive blood, especially in terms of more than 7 weeks of pregnancy.