The, 'Rh factor,' is an inherited protein found on the surface of red blood cells. The majority of people have this protein and are called, 'Rh-positive.' Some people; however, do not have protein - they are called, 'Rh-negative.' Rh-negative pregnant women are at risk of having a baby with a potentially dangerous form of anemia called, 'Rh disease.' Treatment can usually prevent Rh disease. Rh disease destroys fetal red blood cells. At one time, it was a leading cause of fetal and newborn death. Lacking treatment, severely affected fetuses are often stillborn. In newborns, Rh disease may result in:
Rh disease is also called Rhesus isoimmunisation, Rh (D) disease, Rhesus incompatibility, Rhesus disease, RhD Hemolytic Disease of the Newborn, or Rhesus D Hemolytic Disease of the Newborn or RhD HDN. Rh disease occurs during pregnancy when there is an incompatibility between the blood types of the mother and baby and is one of the causes of hemolytic disease of the newborn (HDN). Rhesus disease doesn't harm the mother, but it can cause the baby to become anaemic and develop jaundice. If rhesus disease is left untreated, severe cases can lead to stillbirth. In other cases, it could lead to brain damage, learning difficulties, deafness and blindness.
Rh disease does not affect the mother’s health. In America, approximately fifteen-percent of the white population, five to eight-percent of the Hispanic and African-American populations, as well as one to two-percent of the Native-American and Asian populations are Rh-negative. Being Rh-negative does not affect a person's health in any way.
A mother who is Rh-negative and an Rh-positive father might conceive an Rh-positive baby. When this happens, some of the fetus's Rh-positive red blood cells might get into the mother’s bloodstream during pregnancy, labor and birth. Because red blood cells containing Rh factor are foreign to the mother’s system, her body attempts to fight them by producing antibodies against them - something referred to as, 'sensitization.'
After a women becomes sensitized, her Rh antibodies may cross the placenta and destroy some of the red blood cells of an Rh-positive fetus. In a first pregnancy with an Rh-positive baby, there are commonly no serious issues because the baby is often times born before the mother is sensitized, or at leas before the mother produces large numbers of Rh antibodies. A woman who is sensitized; however, continues to produce Rh antibodies for the rest of her life. What this means is that in a second or later pregnancy, an Rh-positive baby is at risk for more severe Rh disease.
A simple blood test can reveal if a woman is Rh-negative. Every woman should be tested during her first prenatal visit, or prior to pregnancy, in order to find out if she is Rh-negative. Another type of blood test can show if an Rh-negative woman has become sensitized.
A pregnant woman who is unsensitized and Rh-negative can be treated with shots of a purified blood product called, 'Rh immune globulin (RhIg) to prevent sensitization. She most likely will receive RhIg at twenty-eight weeks of pregnancy and again within seventy-two hours of giving birth if a blood test shows that her baby is Rh-positive. The mother does not need an injection after delivery if her baby is Rh-negative. Some health care providers recommend additional RhIg injection if the mother's pregnancy goes beyond her due date. An Rh-negative mother should be treated with RhIg following any situation in which fetal red blood cells can mix in her blood, to include the following:
A woman who is Rh-negative does not need treatment with RhIg if blood tests show that the baby's father is Rh-negative. If the father is Rh-negative, the baby is as well. A baby who is Rh-negative is not at risk of Rh disease.
Why; exactly, RhIg works is not exactly known. It contains antibodies to the Rh factor that might prompt certain immune cells to clear Rh-positive cells from the mother's circulation. As a result, the mother might not have the ability to produce her own antibodies against fetal Rh-positive cells. Protection by RhIg only lasts around twelve weeks. An Rh-negative woman needs to receive treatment during each pregnancy.
Appropriate treatment with RhIg may prevent sensitization in nearly all unsensitized, Rh-negative women. RhIg; however, does not work for an Rh-negative woman who is already sensitized. The primary reason Rh-negative women become sensitized is because they do not receive treatment when needed, such as after an unrecognized miscarriage.
There is no way to get rid of a sensitized mother's antibodies. Even if a woman is healthy and has no symptoms, she may continue to produce antibodies as part of her blood. If she has any more Rh-positive babies, though might develop Rh disease.
The father of the baby can have a blood test to see whether he is Rh-negative or Rh-positive. If the father is Rh-negative, the baby is not at risk of Rh disease and the mother does not require any tests or treatment. If the father is Rh-positive, or if his Rh status is unknown, a health care provider usually offers a sensitized pregnant woman a test called, 'amniocentesis,' to determine whether the baby is Rh-positive or Rh-negative. Even if the father is Rh-positive he might carry an Rh-negative gene. The baby has a fifty-fifty chance of inheriting the Rh-negative gene, so the baby has a fifty-percent chance of being Rh-negative. During amniocentesis, a doctor inserts a needle into the mother's abdomen to withdraw a small amount of amniotic fluid for testing. Amniocentesis presents a very small risk of miscarriage.
A maternal blood test seems to be highly accurate in determining whether the baby is Rh-positive or negative. The blood test was recently introduced in America and might soon reduce the need for amniocentesis. If the baby is Rh-positive, a health care provider measures the levels of antibodies in the mother's blood as her pregnancy progresses. If the mother develops high levels of antibodies, the health care provider may recommend tests that can assist with determining if the baby is developing Rh disease.
If the fetus is near term and tests show the baby is developing anemia, a health care provider might recommend inducing labor early, before the mother's antibodies destroy too many fetal blood cells. After birth, if the baby has jaundice, the baby might receive phototherapy. In some instances, the baby may need a blood transfusion. Some instances of Rh disease are so mild the baby does not require any treatment.
Approximately ten-percent of fetuses with Rh disease develop severe anemia, which in the past was often times fatal. Today, these fetuses may be treated in the uterus as early as eighteen weeks gestation with blood transfusions which are given using cordocentesis. Around ninety-percent of babies who receive treatment now survive.
The incidence of Rh disease in a population depends on the proportion that are rhesus negative. Many non-caucasian peoples have a very low proportion who are Rhesus negative, so the incidence of Rh disease is very low in these populations.
In Caucasian populations about 1 in 10 of all pregnancies are of a Rhesus negative woman with a Rhesus positive baby. It is very rare for the first Rhesus positive baby of a Rhesus negative woman to be affected by Rh disease.
The first pregnancy with a Rhesus positive baby is significant for a rhesus negative woman because she can be sensitized to the Rh positive antigen. In Caucasian populations about 13% of Rhesus negative mothers are sensitized by their first pregnancy with a rhesus positive baby. If it were not for modern prevention and treatment, about 5% of the second Rhesus positive infants of Rhesus negative women would result in stillbirths or extremely sick babies and many babies who managed to survive would be severely ill. Even higher disease rates would occur in the 3rd and subsequent Rhesus positive infants of rhesus negative women. By using anti-RhD immunoglobulin (Rho(D) Immune Globulin) the incidence is massively reduced.
Rh disease sensitization is about 10 times more likely to occur if the fetus is ABO compatible with the mother than if the mother and fetus are ABO incompatible.