When it comes to egg donation, you may be wondering if the blood type of the egg donor matters. While it is not necessary for the donor to have the same blood type as either parent, it’s helpful to understand how blood types work. In this article, we’ll review the blood types, how they are inherited, and when blood type matching matters.
What are blood types?
Blood types are determined by the presence or absence of certain antigens, or proteins, on the surface of our red blood cells. Blood types include A, B, AB, and O. Blood type A has the A antigen, blood type B has the B antigen, blood type AB has both A and B antigens, and blood type O has neither A nor B antigens.
Within each blood type, there is a positive or negative (A+, A-, and so on). The positive or negative sign next to the blood groups is known as the Rhesus (Rh) factor. Rh factor is independent of blood type. It is determined by the presence or absence of a specific antigen on the surface of red blood cells. If a person has the Rh antigen, they are Rh-positive. If they do not have the Rh antigen, they are Rh-negative. Most people, about 85%, are Rh-positive.
According to the San Diego Blood Bank, the average distribution of the blood types in the United States are:
- O Positive (O +): 38%
- O Negative (O -): 7%
- A Positive (A +): 34%
- A Negative (A -): 6%
- B Positive (B +): 9%
- B Negative (B -): 2%
- AB Positive (AB +): 3%
- AB Negative (AB -): 1%
How is a child’s blood type determined in egg donation?
A baby's blood type is determined by the combination of genes inherited from the egg and sperm. Each passes on one of their two ABO alleles to the child. The combination of these alleles determines the baby's blood type. For example, if the egg donor is type A and the biological father (or sperm donor) is type B, the baby could be type A, type B, type AB, or even type O.
Unless both the egg donor and intended father have blood type O, in which case the baby would definitely be type O, you would need a blood test to determine the baby's blood type.
But remember how we said everyone also has an Rh factor, that plus or minus after the letter? A child inherits one Rh allele from the egg donor and one from the intended father. If both are Rh-positive, then the child will be RH-positive. If both are Rh-negative, then the child will be Rh-negative. If one is Rh-negative and the other is Rh-positive, then the child could be either.
Does the egg donor determine the blood type of the child?
The blood type of a child is determined by the combination of genes inherited from the egg and sperm. Each contributes one of two possible alleles (versions) for each gene that codes for the blood type. The Rh blood group system is determined by another gene on chromosome 1 that has two alleles: D and d. The D allele codes for the RhD protein, and the d allele codes for no Rh protein.
While the egg and sperm decide the genetic makeup of the child, they do not have control over the specific alleles that the child inherits. That is determined by the process of meiosis, which randomly selects which sperm or egg cell will fertilize the other.
What is Rh incompatibility?
Rh incompatibility occurs when a pregnant woman (either an intended mother or gestational carrier) who is Rh-negative carries a baby who is Rh-positive. Her immune system may recognize the baby's Rh-positive blood cells as foreign and produce antibodies against them. This can cause her immune system to attack and destroy the baby's red blood cells, leading to a condition called hemolytic disease of the newborn (HDN). HDN can cause serious complications for the baby, including anemia, jaundice, brain damage, and even death.
It’s important to know if you’re at risk for HDN. But the good news is that HDN can be prevented by administering a medication called Rh immunoglobulin (RhIg) or Rhogam to the mother or gestational carrier during pregnancy, which helps prevent her body from making antibodies against the baby's blood cells.
If you or your gestational carrier are Rh negative, consult with your doctor about choosing a donor who is Rh positive.
Is it possible for a child to have a different blood type than both of its parents?
Yup! As you can see in the chart shared above, there are many cases where a child would have a different blood type from their biological parents. For instance, if the egg donor was blood type A and the intended father was type B, the child could be blood type O.
Why would someone want an egg donor with the same blood type?
There are a couple reasons someone might want an egg donor with a specific blood type.
First, they may want to avoid rare blood types in the rare situation that the child would need a blood transfusion. Blood transfusions can only be given to individuals with compatible blood types. For example, if someone with blood type A receives a blood transfusion from someone with blood type B, their body may react negatively and cause serious health issues. Remember though, unless both the egg donor and intended father are type O (in which case the only option is for the child to be type O), there is no guarantee that a child will be the same blood type as one parent.
Second, blood type can also play a role in pregnancy and childbirth. If a mother or gestational carrier is Rh-negative and the baby is Rh-positive, the mother's body may produce antibodies that attack the baby's red blood cells, which can lead to a condition called hemolytic disease of the newborn. However, this is treatable and not a reason to pass on an egg donor.
Third, some parents may want to increase the chances of their child having (or not having) a certain blood type. There is some evidence that certain blood types are more protective against certain health conditions like heart attacks, memory loss, and cancer.
Lastly, parents who do not plan on telling their child about their donor-conceived origins may want to have a child with similar blood type. Although this is your family and you get to decide how / if to tell your story, research has shown over and over the importance of openness and honesty in telling children their conception story and telling it early.
Is it better to find an egg donor who has the same blood type as myself?
So does blood type matter? It is not necessarily "better" to find an egg donor who has the same blood type as yourself. It’s helpful to know the blood type of the donor, but blood type doesn’t need to be a reason to choose a donor, and most parents have other attributes that are more important to them.
As mentioned above, having an egg donor who is the same blood type as the intended mother or gestational carrier can help reduce the risk of Rh incompatibility between the baby and the intended mother, which can cause serious complications for the baby if not treated. However, blood type matching is not necessary for egg donation, and many successful pregnancies and healthy babies are born from egg donation despite not having a blood type match.
Ultimately, the decision of whether to find an egg donor with the same blood type as yourself should be made in consultation with a fertility doctor, who can provide more information and guidance on the risks and benefits of blood type matching in your specific situation.
Cofertility is a human-first fertility ecosystem rewriting the egg freezing and egg donation experience. Our Family by Co platform serves as a more transparent, ethical egg donor matching platform. We are obsessed with improving the family-building journey — today or in the future — and are in an endless pursuit to make these experiences more positive. Create a free account today!
Meera Shah, MD, FACOG, is a double board-certified OBGYN and reproductive endocrinology and fertility specialist at NOVA IVF in Mountain View, California. She is a Founding Medical Advisor at Cofertility. Dr. Shah has authored numerous research articles on topics ranging from fertility preservation, pregnancy loss, reproductive genetics, and ethnic differences in IVF outcomes. Her medical practice incorporates the highest level of evidence-based medicine and the most cutting edge technologies to optimize outcomes for her patients. Dr. Shah applies this approach to her work with Cofertility, ensuring that Cofertility remains up-to-date on latest medical advancements and research in third-party reproduction and reproductive endocrinology in general. When Dr. Shah isn’t busy working with her patients at NOVA IVF, she enjoys playing pretty much any sport, learning new piano pieces on YouTube, and spending quality time with her husband and three boys. You can find her on Instagram providing fertility-related advice and education at @dr_meerashah.
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