1.What is Rh blood group?
There are several classifications of human blood groups, the most common one is ABO blood group classification, and another one is Rh blood group classification. Most people have Rh factor on the surface of their red blood cells, which is called Rh blood group positive, and a few people lack Rh factor on the surface of their red blood cells, which is Rh blood group negative. The Rh-negative blood type of Han Chinese is relatively rare, accounting for only about 3/1000 of the population
2. How is Rh blood type inherited?
The Rh factor depends on the genes of the parents. If the mother’s blood type is Rh negative and the father’s blood type is Rh positive, the child’s blood type can be either Rh positive or Rh negative. If both parents have Rh-negative blood type, the child’s blood type will be Rh-negative and not Rh-positive.
3. Problems faced by Rh-negative pregnant women?
The mother’s own problem: Because of the rare blood type, once the hemorrhage occurs during the delivery period, the blood supply will be tight. Generally the number of Rh-negative blood in stock at blood stations is relatively small, and since ABO blood type matching is also taken into account, the available choices are even smaller. Therefore, for Rh-negative pregnant women who are at risk of hemorrhage, it is very important to make a plan for blood preparation in advance.
4. What are the adverse effects on the fetus?
For Rh-negative mothers, if the child is Rh-negative, there is no problem, but if the child is Rh-positive, it is called “Rh blood group incompatibility”. If the blood of an Rh-positive fetus enters the body of an Rh-negative pregnant woman, it will stimulate her body to produce antibodies against the Rh factor, resulting in “Rh sensitization” of the pregnant woman.
”Rh incompatibility has no effect on the first child because the child is born before the mother has developed enough antibodies in her body. If preventive measures are not taken during the first pregnancy, the mother’s body will produce a lot of antibodies against the Rh factor, and if the fetus is still Rh-positive in the next pregnancy, it will be prone to more serious adverse consequences.
5. Under what circumstances will antibodies be produced in Rh-negative pregnant women?
Under normal circumstances, the blood circulation of the mother and the fetus are relatively isolated from each other, but during pregnancy and delivery, a small amount of fetal blood may enter the mother’s blood circulation. In addition to the delivery process, fetal blood may enter the mother’s system in some cases such as amniocentesis, chorionic villus biopsy, bleeding during pregnancy, external inversion of the breech position, and impact injuries to the abdomen during pregnancy.
Not only full-term pregnancies can cause sensitization in Rh-negative mothers, but if the embryo is Rh-positive, even after spontaneous abortion, ectopic pregnancy, or abortion, the mother may still have Rh antibodies in her body.
6. How does intrauterine hemolysis occur in the fetus?
If an Rh-sensitized mother becomes pregnant again, the Rh antibodies in her body will cross the placenta and enter the body of the Rh-positive fetus, attacking the fetus’ red blood cells and causing destruction of the red blood cells. As the destruction of red blood cells increases, the fetus will develop varying degrees of hemolysis, leading to hemolytic anemia. As the hematocrit level decreases, the fetus will develop local or generalized row of edema, and in severe cases, fetal heart failure or even death will occur.
7.How to monitor the fetus?
Firstly, the mother needs to be examined for the presence of Rh antibodies in her peripheral blood, and the level of antibodies should be monitored regularly.
Secondly, ultrasound examination is needed to find out whether there is intrauterine hemolysis and to determine the degree of intrauterine hemolysis. The main indicators of ultrasound examination are the changes in blood flow in the middle cerebral artery and the edema of the fetus, as well as the thickening and edema of the placenta.
8.How to prevent Rh sensitization?
For Rh-negative pregnant women, Rh immunoglobulin (RhoGAM) can be injected to prevent the production of Rh antibodies so that the next pregnancy with an Rh-positive fetus will not have hemolysis caused by an antigen-antibody reaction. However, if the antibodies have already been produced, the Rh immunoglobulin injection will be useless, so the key is prevention.
9.When should Rh immunoglobulin be injected?
For Rh-negative pregnant women, Rh immunoglobulin injection is required in the following cases.
A.Injected at 28 weeks of gestation to prevent the occurrence of sensitization.
B. In case of delivery of an Rh-positive child, the injection needs to be given within 72 hours.
C.Injected after spontaneous abortion, induced abortion, ectopic pregnancy.
D.Injected after amniocentesis and chorionic villus biopsy.
10.What should be done if the mother is Rh-sensitized and the fetus is Rh-positive?
In addition to regular antibody tests, ultrasonography is needed to determine if there is intrauterine hemolysis and the degree of hemolysis. If the hemolysis is severe, intrauterine blood transfusion may be required and, if necessary, early termination of pregnancy.
11. What are the dilemmas in the management of Rh-negative pregnant women in China?
The most critical drug to prevent sensitization in Rh-negative pregnant women is Rh immunoglobulin (RhoGAM). Since the Rh-negative population in China is relatively small and the amount used is relatively low, foreign pharmaceutical companies are not willing to spend so much time and effort to pass the registration by the Chinese Pharmacovigilance in order to enter the Chinese market.
The current solution to this problem is for patients to purchase the drug themselves from Hong Kong, or to go to a foreign-owned clinic within China for injection.
Until this dilemma is resolved, there are some compromises to help minimize the amount of Rh immunoglobulin we need.
One is to determine the fetus’ Rh blood type in advance by means of a non-invasive fetal DNA test in the mother’s peripheral blood before 28 weeks, and if the fetus is Rh negative, there is no need for Rh immunoglobulin injections.
If the Rh blood type of the fetus cannot be determined in advance, the Rh blood type of the newborn can be determined as soon as possible after birth. Because in principle, Rh immunoglobulin can be injected within 72 hours after delivery, if you know early that the newborn’s Rh blood type is negative, you can have one less injection.