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What is the Rhogam shot?
Simply put, the Rhogam shot is a preparation of an antibody known as Anti-D, derived from human donors, that is given to Rh negative women during pregnancy, or given to an Rh negative male or female after exposure to Rh positive transfusion products.
Remember, I am not a doctor and this is not intended as medical advice. Please discuss what you’ve read here with your OB or Midwife. I do, however, have a Bachelor’s degree and certification in Medical Laboratory Science and have worked as a Blood Bank Technologist.
What is Rh negative?
Red blood cells all contain signals on their surface. If a red blood cell is lacking a specific signal, the body has the ability to create an antibody to the missing signal, much like the body creates an antibody to a foreign virus or bacteria. Some of these red blood cell antibodies are formed naturally, without any stimulation. This means the body never has to see the missing signal to form an antibody against it. That is the case for the signals A and B (Type O blood is a lack of A and B). If you have type A blood, it means you have A signals on your red blood cells and your body has a natural Anti-B floating around. These are very strong and dangerous antibodies, which is why it is important to know your blood type when you get a blood transfusion. Type O is the universal donor because it lacks A and B, thus anyone with Anti-A or Anti-B will not have a problem with type O blood.
Other antibodies are very different, which brings us back to Rhogam. Rhogam is specifically for women with Rh (Rhesus) negative blood, meaning A negative, B negative, O negative, or AB negative. The terms “negative” and “positive’ in this situation mean the presence or lack of another signal, called D in the blood baking world. So, moms with Rh positive blood have the D signal, while moms with Rh negative blood do not have the D signal. The body has the potential to make the Anti-D antibody, but only if stimulated. If this happens, it is called “sensitization.” The body sees the D signal and begins to prepare antibodies against it.
What causes sensitization?
Again, the body is simulated to make Anti-D only when an Rh negative person is exposed to the D signal. This can happen during any exposure to foreign blood, such as during a trauma when an Rh negative person receives O positive blood, or it can happen during pregnancy. Spontaneous mixing of the mother’s blood with the baby’s (this is not a normal, daily occurrence, but it can happen), as well as mixture due to trauma during pregnancy as well as childbirth, allows some of the D positive red blood cells into the mother’s circulation, thus allowing the immune system to respond and sensitization to occur. According to the American Association of Blood Banks, “stimulation can occur with as little as 0.1-1 ml of Rh positive red blood cells” (2). The estimated blood volume of a 150 lb female is 4,423 mL (6). Now, it’s important to note that during the first exposure, usually no damage is done. The body recognizes the D as foreign, and starts manufacturing an antibody against it. The problems occur during the subsequent exposures, if they happen. This is why some women who have had no prenatal care and develop this antibody have no trouble with baby number one, but have great difficulty carrying a baby to term after that.
What are the chances of sensitization?
According the the American Association of Blood Banks, mixing of the mother’s and baby’s blood “occurs spontaneously during pregnancy and it’s likelihood increases with gestational age (3% in 1st trimester, to 12% in the 2nd, and 45% in the 3rd”. Before Rhogam administration, “16% of Rh negative moms with Rh positive infants became sensitized. The rate was < or = 2% ” after Rhogam administration.” The more of mom’s blood that mixes with baby’s blood, the higher the risk of sensitization, which is why it is important to receive the shot after miscarriage, abdominal trauma, and delivery.
What are the dangers of sensitization?
The first pregnancy will usually pose no problems, however, subsequent pregnancies with an Rh positive fetus could result in miscarriage, fatality to the baby later in pregnancy, and extremely high risk pregnancies that require numerous medical interventions (7). This is because the mother’s body is creating an immune response to the baby’s red blood cells, and those antibodies are able to cross the placenta. Once crossed, they attack the baby’s red blood cells, possibly causing miscarriage, severe hemolytic anemia, jaundice, kernicterus, and possible death both before and after delivery. Some of the possible interventions include amniocentesis and numerous intrauterine transfusions (transfusing the fetus with donor red blood cells), as well as continual monitoring and possible early delivery which would include a NICU stay and post birth transfusions (7).
How do I know if I’ve already been sensitized?
A simple test called an antibody screen will detect the Anti-D antibody, and this is routinely done in pregnancy. If you have been sensitized, you and your baby will be monitored very closely.
Can I get the shot after sensitization?
If you have become sensitized and are creating Anti-D, which will be detected in an antibody screen, Rhogam is no longer indicated, nor effective. That is why it is given before, even if in the end it may not be needed. Once sensitization occurs, it is too late, and all future pregnancies of Rh positive babies will be susceptible to serious complications.
Who needs Rhogam?
Going back to basic genetics, an Rh negative person can only give the genes for an Rh negative blood type to their child. An Rh positive person, however, can either give an Rh positive gene, or an Rh negative gene, depending on their specific genetics. If the father is Rh positive, and passes the Rh positive gene to baby, baby will be Rh positive, as it only takes one Rh positive gene to create the D signal. If baby is Rh positive, this creates the situation where Rhogam is indicated for an Rh negative mom. Again, only if the baby is Rh positive will an Rh negative mom need Rhogam; however, without invasive testing it is impossible to know if baby is Rh positive or negative until birth when dad is Rh positive.
I tested Rh positive, but I am being told i still need the shot?
There is something called Weak D, where the D signal is missing a large portion of it’s usual structure. This is a genetic condition. The blood will still type as Rh positive, however anti-D can be formed against the missing pieces of structure. In most hospitals this is a situation where Rhogam may be indicated.
How does Rhogam work?
Rhogam is the very anti-D antibody we are trying to suppress the body from creating, so why is this helpful? If something happens and baby’s blood cells get into mom’s circulation, mom’s body could potentially see those Rh positive baby cells and begin mounting the immune response. However, if the Rhogam anti-D antibodies are already in circulation, they will bind to the baby’s Rh positive cells, and that antibody-red blood cell complex is then taken out of circulation by the body, avoiding the immune response altogether.
So, long long story short, Rhogam is a prepared antibody that will bind any fetal red blood cells that escape into mom’s circulation, preventing a dangerous immune response from happening and protecting any future pregnancies.
Is it a vaccine?
In fact, the Rhogam shot is the complete opposite of a vaccine. As stated earlier, the antibodies in the shot bind fetal red blood cells in mom’s circulation before the body can mount an immune response, thus avoiding immune activation and antibody production. Vaccines, on the other hand, are designed to force the body into mounting a very strong immune response to a foreign invader, so it is able to recognize that invader in the future.
What if Dad is Rh negative?
If the father is Rh negative, he will pass on the gene for Rh negative blood and there is no need for Rhogam.
What is baby is Rh negative?
If baby is truly Rh negative, their blood type is compatible with mom and Rhogam is not indicated. Most hospitals screen the blood type of any infant born to an Rh negative mother; if baby is Rh negative, no Rhogam is needed after birth. If baby is Rh positive, a properly measured dose is given. There is no way to know a baby’s blood type during pregnancy (if dad is Rh positive) without invasive testing, which is not routinely done and poses far more risk than usually necessary.
Is it safe for my baby?
The amount of substance in the Rhogam shot is tiny, 300 micrograms, and should not pose a risk to the baby. It is possible, however, that the anti-D in the Rhogam could attach to the baby’s cells and show up in testing of baby’s blood postpartum, however the implications of that happening are far less dire than sensitization of mom. There is a risk of the ingredients in the shot itself, as well as it’s human origin, which is covered below.
When is it given?
Rhogam is given prophylactically at 28 weeks as a routine shot (5). “The American College of OBs and Gynecologists (ACOG) recommends Rhogam at 28 weeks because 92% of women who develop anti-D do so at or after 28 weeks. Administration during pregnancy reduces sensitization to 0.1% compared to 1.5% if only given postpartum (2)”
Rhogam is given at trauma and miscarriage after 13 weeks and then every 6 weeks following (5).
Rhogam is given after birth if baby is Rh positive within 72 hours (5). According to the American Association of Blood Banks, “about 0.3% of deliveries have a mixing of the mother’s and baby’s blood larger than 30ml (2).”
What are the ingredients?
In the RhoGam brand preservative free product, the final shot contains approximately 5 ± 1% gamma globulin, 2.9 mg/mL
sodium chloride, 0.01% polysorbate 80 and 15 mg/mL glycine.
The product contains no preservative and utilizes a latex-free delivery system (5).
- Gamma globulin–The actual antibody from human donors.
- Sodium chloride–Saline.
- Polysorbate 80–Solubility additive with possible toxicity. There is limited research on this ingredient and it is the most risky and undesirable ingredient in the shot (3). Thankfully, this version of the shot does not have any aluminum or formaldehyde.
- Glycine–An amino acid used as a stabilizer (4).
What are the risks?
The antibodies in the shot are made from human plasma, allowing for a possible infectious risk. However, through the “donor selection process, the fractionation process, the viral filtration step and the viral inactivation process product safety is increased by reducing the risk of transmission of enveloped and non-enveloped viruses (5).”
There is a possible risk of allergic reaction and anaphylaxis, as there is with an foreign substance introduced to the body (5).
According to the package insert, “multiple studies have been performed that prove the safety and efficacy of RhoGAM in both the obstetrical and post transfusion settings (5).”
As you can see, the shot is not without risks, and these must be weighed against the benefits when deciding if the shot is right for you.
How effective is the shot?
“Rho(D) Immune Globulin (Human) administered at 28 weeks, as well as within 72 hours
of delivery, has been shown to reduce the Rh immunization rate to about 0.1-0.2%. (5)”
In a study in 1997, “a control group received
no immunoglobulin therapy after delivery, while the test group received 300 µg of
RhoGAM intramuscularly within 72 hours of delivery of an Rh-positive infant. Six months
after delivery, the incidence of Rh immunization in the control group was 6.4% (32/499)
versus 0.13% (1/781) in the RhoGAM group (p < 0.001) (5).”
In another study, a “single dose of RhoGAM (1.1 mL @ 267 µg/mL) was shown to suppress
anti-D formation after injection of up to 15.1 mL of Rh-positive red cells (5).”
The Rhogam shots definitely appears to do what it is meant to do, which is prevent sensitization.
Should I get it?
That is a decision that is up to you; it’s not one I’ve ever had to make, as I am Rh positive. Although, if I did, I would get it. The ingredients are not perfect, and there are always risks with introducing a foreign substance into your body, especially when you are carrying a child. I know there are women who have had adverse reactions to this shot, and I wish that wasn’t the case.
However, most of these types of decisions are a risk/benefit situation. The shot comes with risks of it’s own, however, the risks of not getting it are there as well and they are extremely dire.
The implications of a woman becoming sensitized and creating anti-D could be detrimental to her ability to ever carry another child to term. Even if the risks of that happening are very small, they still exist, and I’ve seen how dangerous pregnancy can be for the fetus when the mother is sensitized. This is not something that should be taken lightly.
I encourage you to talk to your midwife or OB about your concerns and fears. The best thing to do is be informed, educated, and make the best choice you can so that you have peace about your decision.
- 1. https://www.acog.org/Patients/FAQs/The-Rh-Factor-How-It-Can-Affect-Your-Pregnancy
- 2. AABB Technical Manual References
- AABB Technical Manual
- 3. http://www.thevaccinereaction.org/2016/01/polysorbate-80-a-risky-vaccine-ingredient/
- 4. https://www.webmd.com/vitamins-and-supplements/glycine-uses-and-risks#1
- 5. RhoGAM Package Insert
- 6. https://reference.medscape.com/calculator/estimated-blood-volume
- 7. http://www.stanfordchildrens.org/en/topic/default?id=rh-disease-90-P02498
- 8. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC539316/