Rh Factor and Pregnancy
A blood test in early pregnancy is done to determine your blood type and Rh factor. Read on to learn more about why this is done and what impact Rh factor can have in pregnancy.
Blood Type and Rh Factor
Blood can be classified into four types:
O
A
B
AB
Rh factor is a protein that is found on the surface of red blood cells in most people. Those who have this protein are considered Rh positive, while those who do not have it are Rh negative. So, an O blood type, for example, can be further classified into either O+ or O-, depending on whether a person has this protein or not.
Rh Incompatibility
I want to emphasize that being Rh- is not an illness and normally isn’t an issue, but it can have an effect on pregnancy. When a pregnant person is Rh-, there is a possibility of what is called Rh incompatibility. Rh incompatibility occurs when an Rh- pregnant person is carrying an Rh+ fetus.
And, With rh incompatability, the concern is possible Rh sensitization.
Rh sensitization in pregnancy occurs when an Rh+ baby’s blood enters the bloodstream of the pregnant parent that is Rh-. This exposure can trigger the production of antibodies against the Rh factor by the pregnant person's immune system, which recognizes the Rh factor as foreign and produces antibodies to attack it. Once sensitized, the immune system will produce antibodies against the Rh factor in response to any future exposure to Rh-positive blood. And by future exposures, I mean future pregnancies.
While Rh sensitization will most likely not impact the pregnancy in which it occurs, there are precautions we can take to avoid problems in any subsequent pregnancies. There is a way to prevent Rh sensitization from ever occurring. An Rh immunoglobulin injection can be given to stop the production of antibodies that attack Rh-positive blood cells. RhoGAM is a common brand name for this drug, though there are others.
Now, let’s take a look at a diagram and an example to make sure all of this makes sense.
I’m going to use myself as the example, because I happen to be Rh-. If I was Rh+, as you can see on this diagram, there is no possibility of Rh incompatibility. It wouldn’t matter if my husband was Rh+ or Rh-, and it wouldn’t matter if my baby was Rh+ or Rh-.
If both my husband and I were Rh-, we know that our baby would also be Rh-. There would be no issues with Rh incompatibility in this case, either. My husband happens to be Rh+, so there was a possibility of Rh incompatibility during each of my three pregnancies.
A baby’s blood type is usually unknown until after birth, so I received a RhoGAM injection at around 26-28 weeks in each pregnancy as a precaution. It’s possible for Rh sensitization to occur in the final weeks of pregnancy as the placenta starts to thin. If this happened, the RhoGAM shot would stop my blood from making antibodies that attack Rh-positive blood cells.
After each birth, my baby’s blood was checked after birth to determine if the Rh factor was present. Two of my babies were Rh-, so there was no Rh incompatibility and no possibility of Rh sensitization. No additional precautions were necessary. My second baby was Rh+, so I did receive a RhoGAM injection at some point within a 72 hour window after she was born, as Rh sensitization can also occur during the birth process.
Important Notes
If there is any uncertainty over the father/ non-gestational parent/ sperm donor’s Rh status, Rh incompatibility is a possibility.
While the Rh factor of a gestational surrogate does not have an impact on determining the baby’s Rh factor, it can still impact the pregnancy. Rh incompatibility is a possibility if the gestational surrogate is Rh-.
Rh Sensitization
Had I not received RhoGAM with my second baby, it most likely wouldn’t have been an issue for her. But it could’ve affected my third pregnancy. Without the precautionary RhoGAM, I would have about a 1 in 5 chance of becoming Rh sensitized. Once that happens, RhoGAM is no longer an effective option. It can stop Rh sensitization from occurring, but it can’t help once Rh sensitization has occurred.
I was also screened for Rh antibodies (via a blood test) during each pregnancy just to make sure that sensitization hasn’t occurred at some point in the past. If those antibodies were present and if my third baby was Rh+, my antibodies would cross through the placenta and attack my baby’s blood cells. This results in a potentially serious type of blood disorder called Hemolytic Disease of the Newborn (HDN), which can cause anemia, jaundice, and other complications. There are treatments available for this, the specifics of which will depend on the seriousness of the condition.
I also want to note that There are other situations where Rh sensitization is possible. Here’s a list from ACOG:
Ectopic pregnancy, miscarriage, or abortion
Amniocentesis, CVS, or fetal blood sampling
fetal surgery
Bleeding during pregnancy
Trauma to the abdomen during pregnancy
External cephalic version, which is an attempt to manually turn a baby that is in a breech position
An injection of RhoGAM may be appropriate after the occurrence any of those listed situations.
Talk to Your Care Provider
This situation isn’t going to be relevant for most people (only around 15% are Rh-). But, if you are Rh- and Rh incompatibility is possible (or if Rh sensitization has already occurred), talk to your care provider about your options and how all of this applies to you, specifically.
Interested in learning more about prenatal care? Check out my Proactive Pregnancy: Early Essentials for Expectant Parents toolkit by clicking the button below.